Revert "[28.x] use 28.x branch by default" #1211

Job	Run time
generate-matrix	4s
build (centos-9, aarch64)	1m 25s
build (centos-10, aarch64)	1m 27s
build (debian-bullseye, amd64)	1m 29s
build (centos-9, amd64)	1m 25s
build (debian-bullseye, armhf)	1m 27s
build (centos-10, amd64)	1m 27s
build (debian-bookworm, aarch64)	1m 27s
build (debian-bullseye, aarch64)	1m 27s
build (debian-bookworm, amd64)	1m 31s
build (debian-trixie, aarch64)	1m 28s
build (debian-trixie, armhf)	1m 28s
build (fedora-41, aarch64)	1m 26s
build (debian-bookworm, armhf)	1m 28s
build (debian-trixie, amd64)	1m 30s
build (fedora-43, amd64)	1m 27s
build (fedora-41, amd64)	1m 27s
build (fedora-42, amd64)	1m 30s
build (raspbian-bullseye, armhf)	1m 27s
build (fedora-42, aarch64)	1m 26s
build (ubuntu-jammy, amd64)	1m 29s
build (raspbian-bookworm, armhf)	1m 27s
build (ubuntu-jammy, armhf)	1m 27s
build (ubuntu-noble, aarch64)	1m 29s
build (fedora-43, aarch64)	1m 32s
build (rhel-10, aarch64)	1m 32s
build (ubuntu-plucky, armhf)	1m 28s
build (ubuntu-plucky, amd64)	1m 28s
build (rhel-9, amd64)	1m 28s
build (rhel-9, aarch64)	1m 30s
build (rhel-8, amd64)	1m 28s
build (ubuntu-noble, armhf)	1m 26s
build (rhel-10, amd64)	1m 30s
build (ubuntu-noble, amd64)	1m 27s
build (ubuntu-jammy, aarch64)	1m 28s
build (rhel-8, aarch64)	1m 28s
build (ubuntu-plucky, aarch64)	1m 29s
	52m 52s

Provide feedback