Renamer: reinstate the template haskell level check in notFound

This reinstates a staging check removed in 217caad1 which caused issue #26099 (closed).

One alternative here is to actually make the TcRnBadlyLevelledType warning in checkCrossLevelLiftingTy an error which is not possible without breaking a lot of users. So we continue and bail out later if we must.

Resolves #26099 (closed)

Checklist

• if your MR touches base (or touches parts of ghc-internal used or re-exported by base) more substantially than just amending comments or documentation, you likely need to raise a CLC proposal before merging it.
• if your MR may break existing programs (e.g. causes the compiler to reject programs), please describe the expected breakage and add the user-facing label. This will run ghc/head.hackage> to characterise the effect of your change on Hackage.
• ensure that your commits are either individually buildable or squashed
• ensure that your commit messages describe what they do (referring to tickets using #NNNN syntax when appropriate)
• have added source comments describing your change. For larger changes you likely should add a [Note][notes] and cross-reference it from the relevant places.
• add a [testcase to the testsuite][adding test].
• updates the users guide if applicable
• mentions new features in the release notes for the next release