Do not define our own mpfr_sinpi/mpfr_cospi for mpfr 4.2.0 and later #4

Job	Run time
build-native	5m 2s
build-aarch64	5m 25s
test-native	9m 16s
build-armhf	1m 24s
build-ppc64el	2m 1s
build-s390x	1m 37s
test-aarch64 (qemu_cpu: "max,sve=off")	17m 3s
test-aarch64 (qemu_cpu: "max,sve=on,sve128=on")	22m 15s
test-aarch64 (qemu_cpu: "max,sve=on,sve256=on")	26m 23s
test-aarch64 (qemu_cpu: "max,sve=on,sve512=on")	20m 24s
test-armhf (qemu_cpu: "max")	6m 15s
test-ppc64el (qemu_cpu: "power10")	30m 56s
test-s390x (qemu_cpu: "")	21m 32s
	2h 49m 33s

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