community/mirage: remove redundant sources

These were apparently only used by older versions of Mirage, so
remove them. See CONTRIBUTING.md in upstream's repository.
7 jobs for !21005 with mirage-fixes in 1 minute and 49 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Lint
passed #383026
docker-alpine x86_64
lint

00:00:19

 
  Build
passed #383031
docker-alpine ci-build aarch64
build-aarch64

00:01:29

passed #383032
docker-alpine ci-build armv7
build-armv7

00:01:10

passed #383030
docker-alpine ci-build ppc64le
build-ppc64le

00:01:27

passed #383029
docker-alpine ci-build s390x
build-s390x

00:01:27

passed #383028
docker-alpine ci-build x86
build-x86

00:00:47

passed #383027
docker-alpine ci-build x86_64
build-x86_64

00:00:39