community/py3-pip: simplify, remove dependencies that pip bundles

this makes it almost completely usable as a PEP517-compliant builder
7 jobs for !17496 with py3-pip in 5 minutes and 25 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Lint
passed lint #336270
docker-alpine x86_64

00:00:18

 
  Build
passed build-aarch64 #336275
docker-alpine ci-build aarch64

00:01:10

passed build-armv7 #336276
docker-alpine ci-build armv7

00:01:19

passed build-ppc64le #336274
docker-alpine ci-build ppc64le

00:04:56

passed build-s390x #336273
docker-alpine ci-build s390x

00:00:43

passed build-x86 #336272
docker-alpine ci-build x86

00:00:49

passed build-x86_64 #336271
docker-alpine ci-build x86_64

00:01:04