Fix PickleCoder.as_deterministic_coder() raising TypeError

[AmirF194]

PickleCoder.as_deterministic_coder() and _MemoizingPickleCoder.as_deterministic_coder() both construct FastPrimitivesCoder with a requires_deterministic keyword argument:

def as_deterministic_coder(self, step_label, error_message=None):
  return FastPrimitivesCoder(self, requires_deterministic=step_label)

FastPrimitivesCoder.__init__(self, fallback_coder=PickleCoder()) has never accepted that argument, so both raise TypeError unconditionally. The bug goes back to commit 9be70c9, which changed PickleCoder.as_deterministic_coder from the working DeterministicFastPrimitivesCoder(self, step_label) to this broken call, in the same diff that added a requires_deterministic kwarg to a different class (coder_impl.FastPrimitivesCoderImpl, the Cython impl, not the coders.FastPrimitivesCoder wrapper referenced here). _MemoizingPickleCoder later copied the already-broken line.

The invariant as_deterministic_coder() is supposed to hold, that it always returns a working deterministic coder rather than raising, is exactly what FastPrimitivesCoder's own as_deterministic_coder already does by delegating to _update_compatible_deterministic_fast_primitives_coder. This PR routes both call sites through that same helper instead.

A reachable consumer: GroupByEncryptedKey.expand() calls coder.as_deterministic_coder(...) inside except ValueError, expecting a non-deterministic key to log a warning. When the coder resolves to PickleCoder/_MemoizingPickleCoder, the uncaught TypeError crashes pipeline construction instead.

Verified:

• PickleCoder().as_deterministic_coder('x') and _MemoizingPickleCoder().as_deterministic_coder('x') raise TypeError on master, confirmed live against the installed apache-beam package (byte-identical coders.py) and against this branch.
• New PickleCoderTest.test_as_deterministic_coder fails on master, passes on this branch, both runs in the same container.
• coders_test.py, typecoders_test.py, and fast_coders_test.py (the standard-coder correctness suite, all classes including FastPrimitivesCoder/DeterministicFastPrimitivesCoder) pass unchanged.
• ruff check and yapf --diff are clean on both changed files.
• Not checked: the Cython (coder_impl) fast paths, since this fix is confined to the plain-Python coders.py wrapper layer and does not touch coder_impl.

Fixes #39942

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