Reject CaseSensitive on predicate types that don't support it

[saditya370]

Summary

FilterPredicate.validateCaseSensitivity() only rejected a CaseSensitive value when it was true. A false value on a predicate type that doesn't support case sensitivity (e.g. exists, matches) passed validation and was sent to the API, which ignores it and returns null. Any client that round-trips the response — like terraform-provider-opslevel — then sees the value it set silently disagree with the API, surfacing in Terraform as "Provider produced inconsistent result after apply".

This drops the && *filterPredicate.CaseSensitive clause so Validate() rejects any non-nil CaseSensitive (true or false) for these types. nil remains valid (handled by the existing early return).

Changes

• filters.go — validateCaseSensitivity now rejects any non-nil CaseSensitive on knownNotCaseSensitiveTypes, with a comment explaining the API ignores/nulls the value. Error message unchanged.
• filters_test.go — new table-driven TestFilterPredicateValidateCaseSensitivity exercising Validate() end to end: nil/true/false on a not-case-sensitive type (repository_ids + exists) and true/false on a case-sensitive type (language + equals).
• .changes/unreleased/ — changie Bugfix entry.

Verification

• New false-value test case fails before the code change and passes after.
• go test -race ./... → ok
• gofumpt -d -e . → clean; golangci-lint run → 0 issues

Refs

• OpsLevel support ticket #15041
• terraform-provider-opslevel PR #659 (reviewer request to update validateCaseSensitivity to catch nil-returning cases)