LoopyKeyBuilder: remove update_for_frozenset #3033

Job	Run time
Tests for downstream project Firedrake	15m 44s
Tests for downstream project arraycontext	3m 26s
Tests for downstream project meshmode	14m 56s
Documentation	2m 17s
Tests for downstream project grudge	8m 45s
Conda Examples	2m 45s
Flake8	20s
Tests for downstream project pytential	46m 48s
Mypy	2m 10s
Tests for downstream project pytato	5m 41s
Conda Pytest (ubuntu-latest)	4m 58s
Pylint	2m 28s
Conda Pytest (macos-latest)	10m 30s
Conda Pytest with Intel CL	4m 22s
Conda Pytest without arg check	5m 1s
Conda Pytest Twice (for cache behavior)	6m 6s
	2h 16m 17s

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