ewaol-distro/runc-opencontainers: Switch to main branch

The upstream project has changed from master -> main, so we update
our branch to match .. otherwise, we fail the fetch!

Change based on https://git.yoctoproject.org/meta-virtualization/commit/?h=hardknott&id=724e26aaab925372c89080669256feab2d639b05



Issue-Id: SCM-4066
Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>
Change-Id: Ifcdeb96d47a083e55f31d6c360a75c3610818c8e