Remove unnecessary either (#536)

Author: tom-tan

schema_salad/metaschema/link_res.yml

@@ -2,7 +2,7 @@
   ## Link resolution
 
   The schema may designate one or more fields as link fields that reference other
-  objects.  Processing must resolve links to either absolute URIs using the
+  objects.  Processing must resolve links to absolute URIs using the
   following rules:
 
   * If a reference URI is prefixed with `#` it is a relative

schema_salad/tests/metaschema-pre.yml

@@ -18,7 +18,7 @@
             "```\n\nThis becomes:\n\n```\n",
             "{\n  \"id\": \"http://example.com/base\",\n  \"form\": {\n    \"id\": \"http://example.com/base#one\",\n    \"things\": [\n      {\n        \"id\": \"http://example.com/base#one/two\"\n      },\n      {\n        \"id\": \"http://example.com/base#three\"\n      },\n      {\n        \"id\": \"http://example.com/four#five\",\n      },\n      {\n        \"id\": \"http://example.com/acid#six\",\n      },\n      {\n        \"subscopeField\": {\n          \"id\": \"http://example.com/base#one/thisIsASubscope/seven\"\n        }\n      }\n    ],\n  }\n}\n",
             "```\n",
-            "## Link resolution\n\nThe schema may designate one or more fields as link fields that reference other\nobjects.  Processing must resolve links to either absolute URIs using the\nfollowing rules:\n\n* If a reference URI is prefixed with `#` it is a relative\nfragment identifier.  It is resolved relative to the base URI by setting\nor replacing the fragment portion of the base URI.\n\n* If a reference URI does not contain a scheme and is not prefixed with `#`\nit is a path relative reference.  If the reference URI contains `#` in any\nposition other than the first character, the reference URI must be divided\ninto a path portion and a fragment portion split on the first instance of\n`#`.  The path portion is resolved relative to the base URI by the following\nrule: if the path portion of the base URI ends in a slash `/`, append the\npath portion of the reference URI to the path portion of the base URI.  If\nthe path portion of the base URI does not end in a slash, replace the final\npath segment with the path portion of the reference URI.  Replace the\nfragment portion of the base URI with the fragment portion of the reference\nURI.\n\n* If a reference URI begins with a namespace prefix declared in `$namespaces`\nfollowed by a colon `:`, the prefix and colon must be replaced by the\nnamespace declared in `$namespaces`.\n\n* If a reference URI is an absolute URI consisting of a scheme and path,\nno processing occurs.\n\nLink resolution must not affect the base URI used to resolve identifiers\nand other links.\n\n### Link resolution example\n\nGiven the following schema:\n\n```\n",
+            "## Link resolution\n\nThe schema may designate one or more fields as link fields that reference other\nobjects.  Processing must resolve links to absolute URIs using the\nfollowing rules:\n\n* If a reference URI is prefixed with `#` it is a relative\nfragment identifier.  It is resolved relative to the base URI by setting\nor replacing the fragment portion of the base URI.\n\n* If a reference URI does not contain a scheme and is not prefixed with `#`\nit is a path relative reference.  If the reference URI contains `#` in any\nposition other than the first character, the reference URI must be divided\ninto a path portion and a fragment portion split on the first instance of\n`#`.  The path portion is resolved relative to the base URI by the following\nrule: if the path portion of the base URI ends in a slash `/`, append the\npath portion of the reference URI to the path portion of the base URI.  If\nthe path portion of the base URI does not end in a slash, replace the final\npath segment with the path portion of the reference URI.  Replace the\nfragment portion of the base URI with the fragment portion of the reference\nURI.\n\n* If a reference URI begins with a namespace prefix declared in `$namespaces`\nfollowed by a colon `:`, the prefix and colon must be replaced by the\nnamespace declared in `$namespaces`.\n\n* If a reference URI is an absolute URI consisting of a scheme and path,\nno processing occurs.\n\nLink resolution must not affect the base URI used to resolve identifiers\nand other links.\n\n### Link resolution example\n\nGiven the following schema:\n\n```\n",
             "{\n  \"$namespaces\": {\n    \"acid\": \"http://example.com/acid#\"\n  },\n  \"$graph\": [{\n    \"name\": \"ExampleType\",\n    \"type\": \"record\",\n    \"fields\": [{\n      \"name\": \"link\",\n      \"type\": \"string\",\n      \"jsonldPredicate\": {\n        \"_type\": \"@id\"\n      }\n    }]\n  }]\n}\n",
             "```\n\nProcess the following example:\n\n```\n",
             "{\n  \"$base\": \"http://example.com/base\",\n  \"link\": \"http://example.com/base/zero\",\n  \"form\": {\n    \"link\": \"one\",\n    \"things\": [\n      {\n        \"link\": \"two\"\n      },\n      {\n        \"link\": \"#three\",\n      },\n      {\n        \"link\": \"four#five\",\n      },\n      {\n        \"link\": \"acid:six\",\n      }\n    ]\n  }\n}\n",