fixed: res in plot_partial_wave #430

Job	Run time
conda install latest tensorflow (ubuntu-20.04)	15m 35s
Unit tests (ubuntu-20.04, 3.7)	22m 58s
Build documentation	2m 25s
conda install (ubuntu-20.04)	4m 21s
Test uproot3 (ubuntu-20.04, 3.7)	16m 29s
Unit tests (macos-11, 3.7)	23m 15s
Unit tests (ubuntu-20.04, 3.6)	17m 19s
Unit tests (ubuntu-20.04, 3.8)	14m 55s
Style checks	3m 11s
Coverage (ubuntu-20.04, 3.7)	14s
	2h 0m 42s

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