cyclocomp warning when not using cyclocomp_linter

[TimTaylor]

https://github.com/r-lib/lintr/commit/fdb001c4a5e63dced8d123c1d6f8527e41fdec21 moved the cyclocomp namespace check which now means having a .lintr.R file like the following

linters <- all_linters(
    indentation_linter(indent = 4L),
    cyclocomp_linter = NULL
)

causes a package check to become somewhat noisy and confusing, e.g.

lintr::lint_package()
#> Warning message:
#> Warning encountered while loading config:
#> Caused by warning:
#> ! Cyclocomp complexity is computed using `cyclocomp::cyclocomp()`.
#> ℹ Please install the needed cyclocomp package. 

Only noticed this change today whilst playing with the dev version of lintr. Any chance this could be improved?