_R_CHECK_LENGTH_1_CONDITION_ not needed after R 4.2.0

[infotroph]

User-visible changes in R 4.2 included:

Calling if() or while() with a condition of length greater than one gives an error rather than a warning. Consequently, environment variable _R_CHECK_LENGTH_1_CONDITION_ no longer has any effect.

In a future version bump when we stop testing R < 4.2.0, we can stop setting _R_CHECK_LENGTH_1_CONDITION_ in ci.yml and elsewhere.

[Sweetdevil144]

I guess the following checks are present only in .github/workflows/ci-weekly.yml and .github/workflows/ci.yml.
Also, I guess the behavior controlled by R_CHECK_LENGTH_1_CONDITION is now the default behavior, and thus the environment variable no longer has any effect.
What are your views regarding this @infotroph ?

[infotroph]

It's the default from R 4.2.0 onward, but since we still support R 4.1 (and in fact that's the main version we test on!), I don't think we're ready to remove these yet.