Ignore obsolete usages in the enum extensions

[andrewlock]

Ignore CS0618 and CS0612

By necessity, the extension methods reference all the members of an enum, so we end up triggering obsolete warnings. In general, these warnings won't be useful, so explicitly ignore them

Fixes #97

[github-actions]

Test Results

    254 files  ±  0      254 suites  ±0   12m 40s ⏱️ + 2m 13s
  4 005 tests + 10    3 993 ✅ + 10   12 💤 ±0  0 ❌ ±0 
114 360 runs  +130  114 132 ✅ +130  228 💤 ±0  0 ❌ ±0 

Results for commit c35215f. ± Comparison against base commit dd27676.

♻️ This comment has been updated with latest results.