MNT: Update versions of checkout and setup-miniconda actions

[jbellister-slac]

Before looking too much into the intermittent failures on mamba setup during the conda-incubator/setup-miniconda, update the action to the latest version. Updates checkout action too.

Have seen recently among others:

Error: The process '/usr/share/miniconda3/condabin/mamba' failed with exit code 1

error    libmamba Error when extracting package: Could not chdir include/openssl/rsaerr.h
openssl-1.1.1w-hd590300_0.conda extraction failed
Found incorrect download: openssl. Aborting

etc...

Will make a separate issue if they continue.