ClangImporter/ImportType: fix unused variable warning (#62994)

Exact warning text:
```
ImportType.cpp:2948:12: warning: variable 'numEffectiveParams' set but not used [-Wunused-but-set-variable]
  unsigned numEffectiveParams = params.size();
```

Author: MaxDesiatov

lib/ClangImporter/ImportType.cpp

@@ -2944,10 +2944,6 @@ ImportedType ClangImporter::Implementation::importMethodParamsAndReturnType(
     swiftParams.push_back(var);
   };
 
-  // Determine the number of parameters.
-  unsigned numEffectiveParams = params.size();
-  if (errorInfo) --numEffectiveParams;
-
   auto argNames = importedName.getDeclName().getArgumentNames();
   unsigned nameIndex = 0;
   for (size_t paramIndex = 0, e = params.size(); paramIndex != e;