lint: update a name that wasn't capitalized

I've found some docs that don't capitalize the first letter of Valgrind (namely the contributor doc related to investigating native memory leaks). This additional lint should help to fix that grammatical issue.

Author: mahmoud-moursy

index.js

@@ -101,6 +101,7 @@ const plugins = [
       { yes: "RFC" },
       { no: "[Rr][Ff][Cc]\\d+", yes: "RFC <number>" },
       { yes: "Unix" },
+      { yes: "Valgrind" },
       { yes: "V8" },
     ],
   ],