fix(eap): Remove static sample count thresholds

[jan-auer]

The reliability flag is supposed to return the mathematical accuracy
based on the sample rate without other additional heuristics applied.
Currently, the calculation also compares the sample count with a static
threshold (count > 100) and returns low reliability if the count is
below.

Going forward, any checks for a static sample count threshold will be
performed outside of the EAP.

Confidence calculation for aggregations other than AVG will be fixed in
follow-up PRs.

Requires getsentry/sentry#85323
Ref https://github.com/getsentry/eap-planning/issues/192

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
2862	1	2861	11

View the top 1 failed test(s) by shortest run time

tests.web.rpc.v1.test_endpoint_trace_item_table.test_endpoint_trace_item_table_extrapolation.TestTraceItemTableWithExtrapolation::test_count_reliability_backward_compat

Stack Traces | 0.322s run time

Traceback (most recent call last):
  File ".../v1/test_endpoint_trace_item_table/test_endpoint_trace_item_table_extrapolation.py", line 405, in test_count_reliability_backward_compat
    assert (
AssertionError: assert 2 == 1
 +  where 1 = <google.protobuf.internal.enum_type_wrapper.EnumTypeWrapper object at 0x7f7be3e55150>.RELIABILITY_LOW

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