helpers: simplify Uninferable type error message

[SergioChan]

Type of Changes

	Type
✓	🔨 Refactoring

Description

Closes #2760

This simplifies the AstroidTypeError branch in _object_type_is_subclass.

When klass is Uninferable, we already know its exact type from the guard:

if isinstance(klass, util.UninferableBase):

So the error message no longer needs runtime interpolation via type(klass).
The message is now emitted as a static literal while preserving the same text output.

Validation

• python -m pytest tests/brain/test_brain.py -k "isinstance or issubclass"
  • 35 passed, 105 deselected

[SergioChan]

Rebased this PR branch onto current main and force-pushed to resolve the branch divergence.

What changed:

• Reapplied the existing issue fix commit on top of latest main.
• No functional changes beyond the same targeted error-message behavior.

Validation run:

• python -m pytest tests/test_helpers.py -k Uninferable -q (3 passed)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.27%. Comparing base (b4824be) to head (0d6ef31).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3010   +/-   ##
=======================================
  Coverage   93.27%   93.27%           
=======================================
  Files          92       92           
  Lines       11350    11350           
=======================================
  Hits        10587    10587           
  Misses        763      763           

Flag	Coverage Δ
linux	93.14% <ø> (ø)
pypy	93.27% <ø> (ø)
windows	93.25% <ø> (ø)

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Files with missing lines	Coverage Δ
astroid/helpers.py	94.93% <ø> (ø)

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