Some minor fixes and cleanups

[albestro]

Changelog:

• remove hard-coded variants (not used, templates ones are)
• remove duplicated target from Makefile.compilers (70f1ebb)
• added ruff to pyproject.toml
• some formatting and typos fixing

About first point, I currently went for enabling gcc +profiled in the template as it was in the unused hard-coded variants, just because it sounds like a good thing. I'm not sure how much difference it will make, but it can make a difference in terms of cache reuse for future uenv builds. Indeed, AFAICT, spack info gcc reports

Variants:
...
    bootstrap [true]                   false, true
        Enable 3-stage bootstrap
...
    when %gcc+bootstrap
      profiled [false]                 false, true
          Use Profile Guided Optimization

which means that before this PR stackinator was configuring the bootstrapped compiler as gcc+bootstrap~profiled and now it should (implicitly) become gcc+bootstrap+profiled.

Waiting for your comments about this decision, which we can easily revert and keep the bootstrapped compiler as gcc+bootstrap~profiled.