simplify capturing R dependencies message

[statik]

This simplification is based on feedback from @jennybc @gadenbuie on Connect Cloud.

[gadenbuie]

For some context, this is the discussion we had about the use of renv in the shinylive package: posit-dev/r-shinylive#84

We decided that including "with renv" or even mentioning that we "find which packages are being used via renv" creates confusion about whether or not the user needs to be using renv for their project, or have a lock file, etc. In the end we decided that when using renv only for dependency discovery, it causes less confusion to simply say we "automatically detect package dependencies" and leave out the "with renv".