In PR #16327 the `eslint-plugin-mozilla` package was updated so we no
longer have to force-install packages, and the force-install flags for
`npm install` were removed. However, the CI job was missing from this
commit, which we fix here. In general force-installing packages
shouldn't be necessary unless there are problems with dependencies,
which we would like to know about, so especially in the CI job it seems
like a good idea to not force-install packages to catch upcoming defects
early on.
Extends 19526d2322fabd4425688bb7c5504fa9ea015c5c.