Using `meson build` without `setup` have been deprecated, fix warning
message:
'WARNING: Running the setup command as `meson [options]` instead of
`meson setup [options]` is ambiguous and deprecated.
Remove `.git` suffix from river repo in `sources` section as the
suffix make the ci only clone the repo. Without the suffix the ci
checkout the correct commit to build river.
We don't need to remove the suffix from others sources as cloning
the repo and checkout the tag version we want is enough.
