Validate on master errors because of non-explicit Data.List import

I see

| Run Ghc CompileHs Stage1: utils/check-ppr/Main.hs => _validate/stage1/utils/check-ppr/build/Main.o
| Run Ghc CompileHs Stage1: utils/count-deps/Main.hs => _validate/stage1/utils/count-deps/build/Main.o
| Run Ghc CompileHs Stage1: utils/check-exact/Types.hs => _validate/stage1/utils/check-exact/build/Types.o
Command line: ...
===> Command failed with error code: 1

utils/check-ppr/Main.hs:6:8: error: [-Wcompat-unqualified-imports, -Werror=compat-unqualified-imports]
    To ensure compatibility with future core libraries changes
    imports to Data.List should be
    either qualified or have an explicit import list.
  |
6 | import Data.List
  |        ^^^^^^^^^
Command failed
Build failed.

In a validate-flavoured build. @mpickering and I are certain it's due to 81082cf4. The fix is simple, just opening this ticket for tracking purposes and that people don't need to wonder if it's their fault.