Fix handling of positional url helper arguments when format is false

There is no need to subtract one from the path_params size when there is
no format parameter because it is not present in the path_params array.

Fixes #17819.

(cherry picked from commit 1a50be823186082e8b5a29d8e9ea3a289318d9c1)

Conflicts:
	actionpack/CHANGELOG.md