Remove bors-ng #2414

Job	Run time
codegen	1m 5s
clippy	42s
careful	6m 20s
dependencies	29s
loom	1m 34s
docs	21s
miri	21m 22s
features (1.38)	1m 47s
rustfmt	5s
features (nightly)	38s
san	19m 31s
shellcheck	12s
test (1.38, ubuntu-latest)	16m 21s
test (1.38, windows-latest)	25m 37s
test (stable, ubuntu-latest)	12m 44s
test (stable, windows-latest)	20m 46s
test (nightly, ubuntu-latest)	11m 39s
test (nightly, windows-latest)	19m 45s
test (nightly, ubuntu-latest, i686-unknown-linux-gnu)	13m 40s
test (nightly, ubuntu-latest, armv7-unknown-linux-gnueabihf)	17m 33s
test (nightly, ubuntu-latest, armv5te-unknown-linux-gnueabi)	21m 12s
	3h 33m 23s

Provide feedback