x/tools/gopls: `go mod tidy` quick fix does not preserve comments

[stamblerre]

Before:

After:

In this case, accepting the fix to remove an unused dependency deleted a comment from the require block.

[stamblerre]

#38209 changed gopls to use the go command when adding/deleting requires, so I think this has been addressed in the best way possible. I believe that comments will still be deleted, but this is also what the go command would do.