stop testing python2 and node 16 on EL8 #278

Job	Run time
Apache2 tests on Linux	2m 21s
Apache2 tests on macOS	2m 48s
C++ tests on Linux	2m 50s
C++ tests on macOS	4m 1s
Homebrew packaging tests	6m 59s
Nginx tests on Linux	2m 31s
Nginx tests on macOS	3m 4s
Nginx dynamic module tests on Linux	1m 11s
Node.js tests on Linux	25s
Nginx dynamic module tests on macOS	1m 17s
Node.js tests on macOS	26s
Ruby tests on Linux	1m 1s
Source packaging tests	29s
Passenger Standalone tests on Linux	3m 8s
Ruby tests on macOS	1m 14s
Passenger Standalone tests on macOS	4m 19s
	38m 4s

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