simplify .ms heuristic (#4224)

Simplify .ms heuristic for Unix Assembly by just checking that there is no
`/*` string in the file. This is simpler and seems to work with all Unix Assembly
files in GitHub. A synthetic MAXScript file was also tested by adding assembly inside
a multiline comment.

lib/linguist/heuristics.rb

@@ -333,7 +333,7 @@ def call(data)
     disambiguate ".ms" do |data|
       if /^[.'][a-z][a-z](\s|$)/i.match(data)
         Language["Roff"]
-      elsif /(?<!\S)\.(include|globa?l)\s/.match(data) || /(?<!\/\*)(\A|\n)\s*\.[A-Za-z][_A-Za-z0-9]*:/.match(data.gsub(/"([^\\"]|\\.)*"|'([^\\']|\\.)*'|\\\s*(?:--.*)?\n/, ""))
+      elsif !/\/\*/.match(data) && /^\s*\.(?:include\s|globa?l\s|[A-Za-z][_A-Za-z0-9]*:)/.match(data)
         Language["Unix Assembly"]
       else
         Language["MAXScript"]