Match the "formula name in description" on word boundaries

- The regexp for the "check if formula name is used in formula's
  description" cop matches every instance of the formula name if it
  exists, whether it's in a word or not.
- For example, the formula `mon` has the description "Monitor
  hosts/services/whatever and alert about problems". This makes
  `brew audit --strict` complain because it matches "Monitor",
  which isn't the formula name! The formula `pass` has the description
  "Password manager".  Again, the strict audit matches "Password",
  which isn't an issue.
- Instead, this change matches on a word boundary, so it will match
  `mon:`, or `mon `, but not "Monitor", or, for example, "harmony".
- I've changed the tests to account for this change.

Library/Homebrew/rubocops/formula_desc_cop.rb

@@ -40,7 +40,7 @@ module RuboCop
           end
 
           # Check if formula's name is used in formula's desc
-          problem "Description shouldn't include the formula name" if regex_match_group(desc, /^#{@formula_name}/i)
+          problem "Description shouldn't include the formula name" if regex_match_group(desc, /^#{@formula_name}\b/i)
         end
       end
     end

Library/Homebrew/test/rubocops/formula_desc_cop_spec.rb

@@ -120,7 +120,7 @@ describe RuboCop::Cop::FormulaAuditStrict::Desc do
       source = <<-EOS.undent
         class Foo < Formula
           url 'http://example.com/foo-1.0.tgz'
-          desc 'Foo'
+          desc 'Foo: foobar'
         end
       EOS