.github/workflows/tests: use strings for versions
.github/workflows/tests: use strings for versions

Otherwise yaml will parse these as numbers, which can cause problems later.

Signed-off-by: Jan Luebbe <3a82f1ac4ad59607a20f180f1c67ac8ba31ad0d5@pengutronix.de>

rauc/rauc,jluebbe/rauc,jluebbe/rauc,ejoerns/rauc,rauc/rauc,jluebbe/rauc,rauc/rauc,ejoerns/rauc,ejoerns/rauc