Added quotation marks

When signing commits with git commit. User needs to specify the commit message within quotation marks.

Author: OfficialMuffin

content/authentication/managing-commit-signature-verification/signing-commits.md

@@ -36,7 +36,7 @@ If you have multiple keys or are attempting to sign commits or tags with a key t
 
 1. When committing changes in your local branch, add the -S flag to the git commit command:
   ```shell
-  $ git commit -S -m <em>your commit message</em>
+  $ git commit -S -m <em>"your commit message"</em>
   # Creates a signed commit
   ```
 2. If you're using GPG, after you create your commit, provide the passphrase you set up when you [generated your GPG key](/articles/generating-a-new-gpg-key).