Fix overlaying labels with sankey #1444

Job	Run time
Run pre-commit hooks	20s
UI tests on ubuntu-latest with Python 3.9	6m 11s
Pytest on 3.8, Bokeh 2, ubuntu-latest	31m 29s
Pytest on 3.8, Bokeh 3, ubuntu-latest	32m 47s
Pytest on 3.11, Bokeh 2, ubuntu-latest	35m 24s
Pytest on 3.11, Bokeh 3, ubuntu-latest	32m 14s
Pytest on 3.8, Bokeh 2, macos-latest	53m 12s
Pytest on 3.8, Bokeh 3, macos-latest	59m 9s
Pytest on 3.11, Bokeh 2, macos-latest	48m 11s
Pytest on 3.11, Bokeh 3, macos-latest	1h 1m 48s
Pytest on 3.8, Bokeh 2, windows-latest	49m 12s
Pytest on 3.8, Bokeh 3, windows-latest	1h 14m 12s
Pytest on 3.11, Bokeh 2, windows-latest	51m 6s
Pytest on 3.11, Bokeh 3, windows-latest	1h 9m 46s
	10h 5m 1s

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