Fix incorrect regex rendering in MVC controller documentation

This commit fixes the issue where the regex pattern in the reference documentation
was not rendering correctly for the `/projects/{project:[a-z]+}/versions` mapping.

Closes gh-33766

framework-docs/modules/ROOT/pages/web/webmvc/mvc-controller/ann-requestmapping.adoc

@@ -119,7 +119,7 @@ Some example patterns:
 * `+"/resources/*.png"+` - match zero or more characters in a path segment
 * `+"/resources/**"+` - match multiple path segments
 * `+"/projects/{project}/versions"+` - match a path segment and capture it as a variable
-* `+"/projects/{project:[a-z]+}/versions"+` - match and capture a variable with a regex
+* `++"/projects/{project:[a-z]+}/versions"++` - match and capture a variable with a regex
 
 Captured URI variables can be accessed with `@PathVariable`. For example: