Exclude markup.bold from italic fix

This was improperly matching the first half of the possible closing `__`.

Author: infininight

Syntaxes/Markdown (GitHub Italics).tmLanguage

@@ -7,7 +7,7 @@
 	<key>hideFromUser</key>
 	<true/>
 	<key>injectionSelector</key>
-	<string>L:(text.html.markdown - (markup.italic.markdown))</string>
+	<string>L:(text.html.markdown - (markup.italic.markdown | markup.bold.markdown))</string>
 	<key>name</key>
 	<string>Markdown (GitHub Italics)</string>
 	<key>patterns</key>