fix copy_context in ws threadpool #1649

Job	Run time
Build Dash Package	3m 1s
Build on Windows	5m 35s
Detect Relevant Path Changes	5s
Run Backend Callback Tests (Python 3.12)	3m 9s
Lint & Unit Tests (Python 3.12)	3m 12s
Lint & Unit Tests (Python 3.9)	3m 10s
Typing Tests	3m 33s
Main Dash Tests (Python 3.9, Group 1)	6m 43s
Main Dash Tests (Python 3.9, Group 2)	9m 15s
Run Backend Callback Tests (Python 3.9)	3m 8s
Main Dash Tests (Python 3.12, Group 2)	9m 45s
Main Dash Tests (Python 3.12, Group 1)	8m 36s
Main Dash Tests (Python 3.9, Group 3)	6m 36s
Main Dash Tests (Python 3.12, Group 3)	7m 59s
Table Server Tests (Group ${{ matrix.test-group }})	0s
Run Background & Async Callback Tests (Python ${{ matrix.python-version }})	0s
Table Unit/Lint Tests (Python ${{ matrix.python-version }})	0s
DCC Integration Tests (Python ${{ matrix.python-version }}, Group ${{ matrix.test-group }})	0s
WebSocket Tests (Python ${{ matrix.python-version }})	0s
HTML Components Tests (Python ${{ matrix.python-version }})	0s
DCC Lint Tests (Python ${{ matrix.python-version }})	0s
Dash Table Visual Tests	0s
Finalize Percy Snapshots	12s
Consolidated Test Report	10s
Store Build Artifacts	0s
	1h 14m 9s

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