Fix root ownership (#6901)

Without this, builds are done with the docker user.
We do not change ownership, so it means git objects files
are edited as root.

This leads to follow up issues in the repo like:
"insufficient permission for adding an object to repository database .git/objects".

Partial-Fixes: #6900

Signed-off-by: Jean-Philippe Evrard <jean-philippe.evrard+rochepub@external.roche.com>

hack/api-docs/Makefile

@@ -67,6 +67,7 @@ build: image generate $(SOURCES)
 	    $(GIT_MOUNT) \
 		--sig-proxy=true \
 		--rm \
+		--user $(UID):$(GID) \
 		--env "GIT_COMMITTER_NAME=$(shell git config user.name)" \
 		--env "GIT_COMMITTER_EMAIL=$(shell git config user.email)" \
 		--env "GITHUB_TOKEN=$(GITHUB_TOKEN)" \