Sync legends of LayoutPlot #1301

Job	Run time
Run pre-commit hooks	19s
UI tests on ubuntu-latest with Python 3.9	5m 0s
Pytest on 3.8, Bokeh 2, ubuntu-latest	15m 50s
Pytest on 3.8, Bokeh 3, ubuntu-latest	39m 55s
Pytest on 3.11, Bokeh 2, ubuntu-latest	19m 53s
Pytest on 3.11, Bokeh 3, ubuntu-latest	32m 17s
Pytest on 3.8, Bokeh 2, macos-latest	30m 47s
Pytest on 3.8, Bokeh 3, macos-latest	52m 53s
Pytest on 3.11, Bokeh 2, macos-latest	28m 20s
Pytest on 3.11, Bokeh 3, macos-latest	49m 10s
Pytest on 3.8, Bokeh 2, windows-latest	33m 24s
Pytest on 3.8, Bokeh 3, windows-latest	1h 0m 44s
Pytest on 3.11, Bokeh 2, windows-latest	31m 17s
Pytest on 3.11, Bokeh 3, windows-latest	57m 5s
	7h 36m 54s

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