DecomposeComplexOps: update parseEquation to skip space char for AtenEinsumOp op (#2910)

Just a minor update to skip the space char if included in the equation
string

---------

Co-authored-by: Ze Zhang <ze.zhang@getcruise.com>

lib/Dialect/Torch/Transforms/DecomposeComplexOps.cpp

@@ -181,7 +181,7 @@ static bool parseEquation(const std::string &equation,
       inputToken.clear();
       currentVariable = kIsResult;
       index++;
-    } else {
+    } else if (equation[index] != ' ') {
       return false;
     }
     index++;