[troff mode] Remove bogus MIME string

Issue codemirror#3869

Author: marijnh

mode/meta.js

@@ -138,7 +138,7 @@
     {name: "Tiki wiki", mime: "text/tiki", mode: "tiki"},
     {name: "TOML", mime: "text/x-toml", mode: "toml", ext: ["toml"]},
     {name: "Tornado", mime: "text/x-tornado", mode: "tornado"},
-    {name: "troff", mime: "troff", mode: "troff", ext: ["1", "2", "3", "4", "5", "6", "7", "8", "9"]},
+    {name: "troff", mime: "text/troff", mode: "troff", ext: ["1", "2", "3", "4", "5", "6", "7", "8", "9"]},
     {name: "TTCN", mime: "text/x-ttcn", mode: "ttcn", ext: ["ttcn", "ttcn3", "ttcnpp"]},
     {name: "TTCN_CFG", mime: "text/x-ttcn-cfg", mode: "ttcn-cfg", ext: ["cfg"]},
     {name: "Turtle", mime: "text/turtle", mode: "turtle", ext: ["ttl"]},

mode/troff/troff.js

@@ -80,6 +80,5 @@ CodeMirror.defineMode('troff', function() {
 CodeMirror.defineMIME('text/troff', 'troff');
 CodeMirror.defineMIME('text/x-troff', 'troff');
 CodeMirror.defineMIME('application/x-troff', 'troff');
-CodeMirror.defineMIME('troff', 'troff');
 
 });