escape the quotes

Signed-off-by: Matthew Fisher <matt.fisher@fermyon.com>

.github/workflows/code-review.yml

@@ -42,7 +42,7 @@ jobs:
                       },
                       {
                           "role": "user",
-                          "content": "GIT DIFF:\n\n```\n$escaped_diff\n```\n"
+                          "content": "GIT DIFF:\n\n```\n'"$escaped_diff"'\n```\n"
                       }
                   ]
               }')