build: Update to header 1.3.294 #600

Job	Run time
chromium	1m 40s
android (armeabi-v7a)	1m 0s
generate_source	42s
build_and_test (Debug, ubuntu-20.04)	1m 16s
android (arm64-v8a)	52s
build_and_test (Debug, ubuntu-22.04)	1m 9s
reuse	7s
build_and_test (Debug, windows-latest)	1m 25s
windows-arm64	55s
build_and_test (Debug, macos-latest)	53s
build_and_test (Release, ubuntu-20.04)	1m 33s
build_and_test (Release, ubuntu-22.04)	1m 30s
build_and_test (Release, windows-latest)	1m 59s
build_and_test (Release, macos-latest)	1m 11s
	16m 12s

Provide feedback