fix: fix issues with SliderLabel strong reference

[tlambert03]

I found a case where SliderLabel prevented cleanup by holding onto a bound method. This cleans that up

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 87.04%. Comparing base (952ac33) to head (4c57cfd).

Files with missing lines	Patch %	Lines
src/superqt/sliders/_labeled.py	60.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #248 +/- ## ========================================== - Coverage 87.09% 87.04% -0.05% ========================================== Files 46 46 Lines 3433 3436 +3 ========================================== + Hits 2990 2991 +1 - Misses 443 445 +2 ```

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[tlambert03]

this is a real strange mess. The goal is to remove the partial and lambda usage in _labeled... but for some reason, merely commenting out the line:

        if connect is not None:
            self.editingFinished.connect(lambda: connect(self.value()))

in SliderLabel causes a segfault on pyside6.

not urgent, so going back in the pile for now

[Czaki]

@tlambert03 could you point line in code?

[tlambert03]

Sure, basically the goal of this PR is to:

• remove use of partial here
• get rid of connect argument here and the connection that happens in the init here ... instead, having anything that instantiates a SliderLabel worry about doing its own connections.
• in doing that last step, get rid of the lambda here

(apologies for the crappy code...)

[Czaki]

Ah. You do not use tox/nox that makes it harder to reproduce locally.

Could you try to check if store hard reference to connect when commenting out this part of code?
Because commenting out lambda connection means also lost the reference.

[tlambert03]

prefer not to use nox/tox honestly.
however, i don't think it should be hard to reproduce. i just made a new environment, pip installed editable with tests, and installed the pyside6 extra (==6.7) and was able to reproduce it. i'm on mac fwiw.

don't have time to check the references now

[Czaki]

I'm going sleep. If you do not do this, I will try tomorrow.