refactor(dev-infra): always use en-US locale for printing date in merge tool (#42470)
refactor(dev-infra): always use en-US locale for printing date in merge tool (#42470)

In the dev-infra merge tool, a test fails locally if it runs on
a system with a different system locale. We can either make the
test more flexible, or update the merge tool to always print the date
in `en-US` format. The latter is more reasonable given our console
messages being in english anyway.

PR Close #42470

angular/dev-infra,angular/dev-infra,angular/dev-infra,angular/dev-infra