Revert "Don't remove one directory level from slspath"

[dwoz]

This reverts commit 7c28995.

This change is being reverted because it broke states without going through any kind of deprecation path.

What issues does this PR fix or reference?

#56119

Tests written?

Yes

Commits signed with GPG?

Yes

[terminalmage]

That change should absolutely not be reverted. It was a bugfix.

From the documentation:

The slspath variable contains the path to the current sls file. The value of slspath
in files referenced in the current sls depends on the reference method. For jinja
includes slspath is the path to the current file. For salt includes slspath is the path
to the included file.

"the path to the current SLS file". Not a directory.

[thatch45]

Those docs should be fixed, not breaking everyone's states

[terminalmage]

Actually, after looking at the code, I think that we should revert, but not without making other changes. See here for my reasoning on this.