Remove deprecated interruption_strategies plumbing

The interruption_strategies mechanism was deprecated in v0.0.99 in favor
of LLMUserAggregator's user_turn_strategies. All evaluation logic was
already removed — this removes the remaining field definitions, property,
StartFrame propagation, conditional check in base_input.py, strategy
files, and test.

tests/test_interruption_strategies.py

@@ -1,28 +0,0 @@
-#
-# Copyright (c) 2024-2026, Daily
-#
-# SPDX-License-Identifier: BSD 2-Clause License
-#
-
-import unittest
-
-from pipecat.audio.interruptions.min_words_interruption_strategy import MinWordsInterruptionStrategy
-
-
-class TestMinWordsInterruptionStrategy(unittest.IsolatedAsyncioTestCase):
-    async def test_min_words(self):
-        strategy = MinWordsInterruptionStrategy(min_words=2)
-        await strategy.append_text("Hello")
-        self.assertEqual(await strategy.should_interrupt(), False)
-        await strategy.append_text(" there!")
-        self.assertEqual(await strategy.should_interrupt(), True)
-        # Reset and check again
-        await strategy.reset()
-        await strategy.append_text("Hello!")
-        self.assertEqual(await strategy.should_interrupt(), False)
-        await strategy.append_text(" How are you?")
-        self.assertEqual(await strategy.should_interrupt(), True)
-
-
-if __name__ == "__main__":
-    unittest.main()