community: Add deprecation warning for GigaChat integration in langchain-community #33210

Job	Run time
build	15s
cd libs/community / make extended_tests #3.9	3m 36s
cd libs/community / make extended_tests #3.11	3m 15s
cd libs/community / poetry run pytest -m compile tests/integration_tests #3.11	43s
cd libs/community / poetry run pytest -m compile tests/integration_tests #3.9	37s
cd . / make lint #3.9	1m 17s
cd . / make lint #3.12	1m 3s
cd libs/community / make lint #3.13	4m 32s
cd libs/community / make lint #3.9	1m 55s
cd libs/community / make test #3.13	3m 22s
cd libs/community / make test #3.9	1m 3s
test-doc-imports (3.12) / check doc imports #3.12	1m 1s
cd libs/community / make test # pydantic: ~=2.7.0, python: 3.11,	46s
cd libs/community / make test # pydantic: ~=2.8.0, python: 3.11,	42s
cd libs/community / make test # pydantic: ~=2.9.0, python: 3.11,	49s
CI Success	1s
	24m 57s

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