drop pg14 support #363

Job	Run time
push-test-images-for-release	0s
push-test-images-for-dev (citusupgradetester)	3m 54s
prepare_pgversion_matrix	3s
push-test-images-for-dev (pgupgradetester)	2m 19s
push-test-images-for-dev (stylechecker)	2m 25s
push-test-images-for-dev (extbuilder, 15.10)	1m 27s
push-test-images-for-dev (extbuilder, 16.6)	1m 28s
push-test-images-for-dev (extbuilder, 17.2)	1m 27s
push-test-images-for-dev (exttester, 15.10)	3m 44s
push-test-images-for-dev (exttester, 16.6)	3m 55s
push-test-images-for-dev (exttester, 17.2)	3m 54s
push-test-images-for-dev (failtester, 15.10)	2m 27s
push-test-images-for-dev (failtester, 16.6)	2m 4s
push-test-images-for-dev (failtester, 17.2)	2m 19s
	31m 26s

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