Fix \s not matching eol

Author: jdkato

Microsoft/HeadingPunctuation.yml

@@ -5,4 +5,4 @@ nonword: true
 level: warning
 scope: heading
 tokens:
-  - '[a-z0-9][.?!]\s'
+  - '[a-z0-9][.?!](?:\s|$)'

features/rules.feature

@@ -131,7 +131,7 @@ Feature: Rules
       """
       test.md:1:7:Microsoft.HeadingColons:Capitalize ': m'."
       test.md:5:3:Microsoft.Headings:'This is a Heading' should use sentence-style capitalization.
-      test.md:7:11:Microsoft.HeadingPunctuation:Don’t use end punctuation in headings.
+      test.md:7:13:Microsoft.HeadingPunctuation:Don’t use end punctuation in headings.
       test.md:9:15:Microsoft.HeadingAcronyms:Avoid using acronyms in a title or heading.
       """