Remove newline when highlighting random chunks of code

Somewhere when tokenizing a newline gets added to code formatted by chroma. This breaks the case of 'added-code' inside of an 'added-line' in a diff. Just remove any newline when processing chunks of code since we don't need it.

Fixes go-gitea#12172

modules/highlight/highlight.go

@@ -81,7 +81,9 @@ func Code(fileName, code string) string {
 	}
 
 	htmlw.Flush()
-	return htmlbuf.String()
+	// Strip any newline that chroma might have added since this may be one of multiple
+	// highlights on what should display as a single line of code
+	return strings.TrimSuffix(htmlbuf.String(), "\n")
 }
 
 // File returns map with line lumbers and HTML version of code with chroma syntax highlighting classes