Update size of SHA to fix #3538 (#3563)

modules/markdown/markdown.go

@@ -93,7 +93,7 @@ var (
 	// Sha1CurrentPattern matches string that represents a commit SHA, e.g. d8a994ef243349f321568f9e36d5c3f444b99cae
 	// FIXME: this pattern matches pure numbers as well, right now we do a hack to check in RenderSha1CurrentPattern
 	// by converting string to a number.
-	Sha1CurrentPattern = regexp.MustCompile(`\b[0-9a-f]{7,40}\b`)
+	Sha1CurrentPattern = regexp.MustCompile(`\b[0-9a-f]{40}\b`)
 )
 
 // FindAllMentions matches mention patterns in given content