Remove `ThinClient` from `dos/` #130

Job	Run time
android (ubuntu-20.04, x86_64-linux-android)	2m 53s
android (ubuntu-20.04, aarch64-linux-android)	3m 0s
ios (macos-11, aarch64-apple-ios)	10m 38s
android (ubuntu-20.04, i686-linux-android)	3m 7s
ios (macos-11, x86_64-apple-ios)	7m 26s
android (ubuntu-20.04, armv7-linux-androideabi)	3m 21s
ios (macos-11, aarch64-apple-darwin)	6m 23s
ios (macos-11, x86_64-apple-darwin)	8m 41s
error_reporting	0s
	45m 29s

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