Fix nightly Token check

This fixes the scheduled job when it was trying the Token permutation.
The problem is that proc-macro2 is failing for some inputs. In
particular it was having problems with CR in string continuations
(dtolnay/proc-macro2#540).

There probably should be a better mechanism for identifying inputs that
are known to fail and to allow them. This can be difficult with
generated inputs since keeping that list up-to-date can be a challenge.
It would likely be best to have some automated tooling to help with
that.

For now, this just disables the proc-macro2 validation for generated
Token inputs.

Author: ehuss

.github/workflows/daily-grammar-check.yml

@@ -39,7 +39,7 @@ jobs:
       continue-on-error: true
       run: |
         cargo run --release -p grammar-check -- lex-compare --path rust
-        cargo run --release -p grammar-check -- lex-compare --permute Token
+        cargo run --release -p grammar-check -- lex-compare --permute Token --tool rustc_parse
 
     - name: Check for existing open issues
       if: steps.grammar-check.outcome == 'failure'