fix: Avoid multiple audioFocusRequest instances for focus changes #1057

Job	Run time
call-min-flutter-test / android	3m 18s
call-min-flutter-test / ios-16	1s
call-min-flutter-test / test	2m 52s
call-min-flutter-test / ios-17	1s
call-min-flutter-test / macos-14	0s
call-min-flutter-test / linux	3m 17s
call-min-flutter-test / macos-13	1s
call-min-flutter-test / web	3m 16s
call-min-flutter-test / windows	3m 10s
call-test / ios-16	1s
call-test / android	3m 17s
call-test / ios-17	1s
call-test / macos-13	1s
call-test / test	2m 8s
call-test / web	3m 17s
call-test / linux	19s
call-test / macos-14	0s
call-test / windows	8s
	25m 8s

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