docs: fix minor docstring formatting

Google APIs · copybara-github · commit c2674a3456a8 · 2022-08-09T15:55:14.000-07:00
PiperOrigin-RevId: 466493520
diff --git a/google/cloud/documentai/v1/document_schema.proto b/google/cloud/documentai/v1/document_schema.proto
@@ -90,7 +90,7 @@ message DocumentSchema {
     // - name matching is case-insensitive
     // - Maximum 64 characters.
     // - Must start with a letter.
-    // - Allowed characters: ASCII letters [a-z0-9_-].  (For backward
+    // - Allowed characters: ASCII letters `[a-z0-9_-]`.  (For backward
     //   compatibility internal infrastructure and tooling can handle any ascii
     //   character)
     // - The '/' is sometimes used to denote a property of a type.  For example
