Fix: Add regex delimiters to schema_filter to prevent preg_match errors

This commit adds necessary delimiters to regular expressions used in schema_filter configurations, preventing the 'No ending delimiter' error in preg_match. It improves the error handling by ensuring that regular expressions are always correctly formatted.

docs/configuration.rst

@@ -883,7 +883,7 @@ can configure. The following block shows all possible configuration keys:
                 logging:                  "%kernel.debug%"
                 platform_service:         MyOwnDatabasePlatformService
                 auto_commit:              false
-                schema_filter:            ^sf2_
+                schema_filter:            /^sf2_/
                 mapping_types:
                     enum: string
                 types: