[Bugfix] use right truncation for non-generative tasks (#12050)

Signed-off-by: Joe Runde <Joseph.Runde@ibm.com>

tests/entrypoints/llm/test_encode.py

@@ -105,3 +105,10 @@ def test_multiple_pooling_params(llm: LLM):
     # pooling_params is None, default params should be applied
     outputs = llm.encode(PROMPTS, pooling_params=None)
     assert len(PROMPTS) == len(outputs)
+
+
+@pytest.mark.skip_global_cleanup
+def test_right_side_truncation(llm: LLM):
+    # Embeddings models should truncate the end of the prompt
+    tokenizer = llm.get_tokenizer()
+    assert tokenizer.truncation_side == "right"