remove unneeded setting of isPlaying flag #23

Job	Run time
lint	28s
Windows 32-bit	14m 51s
macOS universal	32m 46s
Windows 64-bit	15m 12s
Linux focal gcc7	1m 51s
macOS x64 legacy	18m 53s
Windows 64-bit MinGW	5m 19s
Linux focal gcc9 shared libscsynth	3m 0s
macOS x64 use system libraries	7m 13s
Linux jammy gcc10 use system libraries	2m 13s
macOS x64 shared libscsynth	13m 26s
Linux jammy gcc11	1m 35s
Linux jammy gcc12	2m 19s
Linux focal clang7	1m 57s
Linux focal clang11	2m 17s
Linux focal clang12	1m 45s
Linux jammy clang13	1m 59s
Linux jammy clang14	1m 33s
deploy ${{ matrix.artifact-suffix }} to s3	0s
deploy release	0s
test on ${{ matrix.name }}	0s
	2h 8m 37s

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