opentelemetry-processor-baggage: silence ruff warning

Ruff warns about the following which given the implementation seems safe
to ignore:

E731 Do not assign a `lambda` expression, use a `def`
   |
25 | # A BaggageKeyPredicate that always returns True, allowing all baggage keys to be added to spans
26 | ALLOW_ALL_BAGGAGE_KEYS: BaggageKeyPredicateT = lambda _: True
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ E731
   |
   = help: Rewrite `ALLOW_ALL_BAGGAGE_KEYS` as a `def`

processor/opentelemetry-processor-baggage/src/opentelemetry/processor/baggage/processor.py

@@ -23,7 +23,7 @@
 BaggageKeyPredicateT = Callable[[str], bool]
 
 # A BaggageKeyPredicate that always returns True, allowing all baggage keys to be added to spans
-ALLOW_ALL_BAGGAGE_KEYS: BaggageKeyPredicateT = lambda _: True
+ALLOW_ALL_BAGGAGE_KEYS: BaggageKeyPredicateT = lambda _: True  # noqa: E731
 
 
 class BaggageSpanProcessor(SpanProcessor):