Merge milestone and RC release notes for 5.1

Resolves #1251.

Author: marcphilipp

documentation/src/docs/asciidoc/link-attributes.adoc

@@ -50,6 +50,7 @@ endif::[]
 :EnabledOnOs:                       {javadoc-root}/org/junit/jupiter/api/condition/EnabledOnOs.html[@EnabledOnOs]
 :ExecutionCondition:                {javadoc-root}/org/junit/jupiter/api/extension/ExecutionCondition.html[ExecutionCondition]
 :ExtendWith:                        {javadoc-root}/org/junit/jupiter/api/extension/ExtendWith.html[@ExtendWith]
+:ExtensionContext:                  {javadoc-root}/org/junit/jupiter/api/extension/ExtensionContext.html[ExtensionContext]
 :ExtensionContext_Store:            {javadoc-root}/org/junit/jupiter/api/extension/ExtensionContext.Store.html[Store]
 :ParameterizedTest:                 {javadoc-root}/org/junit/jupiter/params/ParameterizedTest.html[@ParameterizedTest]
 :ParameterResolver:                 {javadoc-root}/org/junit/jupiter/api/extension/ParameterResolver.html[ParameterResolver]

documentation/src/docs/asciidoc/release-notes/index.adoc

@@ -18,12 +18,6 @@ include::../link-attributes.adoc[]
 
 include::release-notes-5.1.0.adoc[]
 
-include::release-notes-5.1.0-RC1.adoc[]
-
-include::release-notes-5.1.0-M2.adoc[]
-
-include::release-notes-5.1.0-M1.adoc[]
-
 include::release-notes-5.0.3.adoc[]
 
 include::release-notes-5.0.2.adoc[]