Our direct dependency on `@actions/exec` was removed in 274ad33,
though we still depend on it indirectly.

We have this dependency anyway (since we're running on Node). This drops
the problematic libsodium dependency so that the Action works on targets
which libsodium doesn't support.

Resolves: #56

The constant variables `cur_dev` and `min_dev` were added but never used in the comparison. This change is assuming this was by mistake. Otherwise `cur_dev` and `min_dev` are unused and should be removed.

Previously it was referencing the wrong group index (off by one), which is easy to do when relying on indices. Using capture groups here should make it less error prone (and also fixes this initial problem).

Long term a small unit test should avoid this happening / regressing.