[ci] remove all pull_request related conditions #1567

Job	Run time
ubuntu_clang (Release, OFF, ON)	2m 2s
ubuntu_clang (Release, OFF, OFF)	1m 54s
ubuntu_clang (Debug, OFF, ON)	2m 20s
ubuntu_clang (Debug, OFF, OFF)	2m 17s
ubuntu_clang_for_liburing (Release, OFF, ON)	1m 54s
ubuntu_clang_for_liburing (Debug, OFF, ON)	2m 15s
ubuntu_clang_pb (Release, OFF, ON)	1m 7s
ubuntu_clang_pb (Release, OFF, OFF)	1m 7s
ubuntu_clang_pb (Debug, OFF, ON)	1m 3s
ubuntu_clang10 (Release)	45s
ubuntu_clang_pb (Debug, OFF, OFF)	1m 10s
ubuntu_clang10 (Debug)	47s
	18m 41s

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