fix(#297): make vocabulary thread-safe and return test-not-verb

[VasilevNStas]

fix #297

Context. The unit-test-is-not-verb lint was disabled in #297 because it occasionally produced NullPointerException when the EO-to-Java Compiler ran lints in parallel. The maintainers agreed to re-enable it once a thread-safety fix lands (see the @todo #297 puzzle left in PkMono).

Root cause: OpenNLP's POSTaggerME is not thread-safe: a single shared instance mutates internal state (bestSequence) on every tag() call. Vocabulary kept one such instance and was invoked from multiple threads building eo-runtime with lints.

Fix:

• Vocabulary now holds a shared POSModel (immutable, safe to reuse) and creates one POSTaggerME per thread via ThreadLocal, so concurrent calls never share mutable tagger state.
• Re-enabled LtTestNotVerb (the unit-test-is-not-verb lint) in MonoLints, so it is back among the active default lints.
• Removed the resolved @todo #297 from PkMono.

Tests: mvn clean install -Pqulice — 578 tests, all green, including the existing concurrent VocabularyTest, LtTestNotVerbTest, and lintsInMultipleThreads.

[VasilevNStas]

@volodya-lombrozo @yegor256 plz review, I've fixed it

[VasilevNStas]

@volodya-lombrozo I`m fixed it
plz re-review