Minor typo

Colon outside of italics in the bug report issue template when in every similar instance of this in this file it is inside.

Signed-off-by: Rillian Grant <rillian.grant@hotmail.com>

.github/ISSUE_TEMPLATE/Bug_report.md

@@ -34,7 +34,7 @@ Tell us what happens instead
 
 ### Server configuration
 
-**Operating system**:
+**Operating system:**
 
 **Web server:**