php-fatal-error.html is now tracked in git

Our gitignore had 'php-*' to ignore all the PHP subdirectories, that
also catched the good old 'php-fatal-error.html' file.

I am not the author of this file, merely copied it from production.

Change-Id: Id4bc5e85f4dd03af4794a9c8ae126d6985d9fb9b