repository_rules.md: also mention the `bazel sync` command
repository_rules.md: also mention the `bazel sync` command

The documentation on repository rules describes the invalidation mechanism
for repository rule. In this context, also mention bazel's `sync` command
as it can also be used to invalidate repositories.

Change-Id: I9df56f56a73ec0d11602bad1ba493365802c401d
PiperOrigin-RevId: 264854678

twitter-forks/bazel,meteorcloudy/bazel,werkt/bazel,dslomov/bazel,perezd/bazel,werkt/bazel,meteorcloudy/bazel,perezd/bazel,safarmer/bazel,werkt/bazel,akira-baruah/bazel,dslomov/bazel-windows,cushon/bazel,akira-baruah/bazel,meteorcloudy/bazel,dslomov/bazel,dslomov/bazel-windows,perezd/bazel,meteorcloudy/bazel,davidzchen/bazel,aehlig/bazel,bazelbuild/bazel,davidzchen/bazel,safarmer/bazel,aehlig/bazel,bazelbuild/bazel,akira-baruah/bazel,cushon/bazel,davidzchen/bazel,davidzchen/bazel,cushon/bazel,aehlig/bazel,perezd/bazel,twitter-forks/bazel,dslomov/bazel-windows,bazelbuild/bazel,ButterflyNetwork/bazel,bazelbuild/bazel,dslomov/bazel-windows,werkt/bazel,dslomov/bazel,dslomov/bazel-windows,akira-baruah/bazel,katre/bazel,meteorcloudy/bazel,safarmer/bazel,davidzchen/bazel,meteorcloudy/bazel,akira-baruah/bazel,aehlig/bazel,twitter-forks/bazel,twitter-forks/bazel,davidzchen/bazel,katre/bazel,ulfjack/bazel,meteorcloudy/bazel,dslomov/bazel,ButterflyNetwork/bazel,twitter-forks/bazel,katre/bazel,katre/bazel,werkt/bazel,ulfjack/bazel,twitter-forks/bazel,akira-baruah/bazel,dslomov/bazel,cushon/bazel,ulfjack/bazel,safarmer/bazel,twitter-forks/bazel,bazelbuild/bazel,aehlig/bazel,perezd/bazel,ButterflyNetwork/bazel,ulfjack/bazel,cushon/bazel,ButterflyNetwork/bazel,dslomov/bazel-windows,ulfjack/bazel,safarmer/bazel,werkt/bazel,ButterflyNetwork/bazel,perezd/bazel,katre/bazel,aehlig/bazel,davidzchen/bazel,safarmer/bazel,ulfjack/bazel,cushon/bazel,ulfjack/bazel,dslomov/bazel,katre/bazel,dslomov/bazel,ButterflyNetwork/bazel,aehlig/bazel,perezd/bazel,bazelbuild/bazel