Add upgrading notes to the new socket file test

Author: JoshuaBehrens

UPGRADING

@@ -467,6 +467,12 @@ PHP 8.2 UPGRADE NOTES
   Previously only hexadecimal prefixes and using a leading 0 for octal numbers
   was supported.
 
+- Parsing of invalid values will now trigger a warning when this was silently
+  ignored before. Interpretation of these values is not changed, for
+  backwards compatibility. Testing configuration can fail though.
+  This affects the following settings:
+  . {fpm_pool}.listen
+
 - Parsing of some ill-formatted values will now trigger a warning when this was
   silently ignored before. Interpretation of these values is not changed, for
   backwards compatibility. This affects the following settings: