fix expected output (#297)

Author: jacobpake

frontend/tests/cases/negative/graded/polySemiring.gr.output

@@ -1,6 +1,6 @@
-Type checking failed:
+Type checking failed: 
 Counter example: frontend/tests/cases/negative/graded/polySemiring.gr:2:1:
   When checking `foo`, (1 : s) + (1 : s) is not approximatable by r for type s
 
 Counter-example:
-  r = 3 :: s
+  r = 3 :: s

frontend/tests/cases/negative/graded/semiringsDontHaveCommutativeMult.gr.output

@@ -3,4 +3,4 @@ Counter example: frontend/tests/cases/negative/graded/semiringsDontHaveCommutati
   When checking `poly`, c * ((1 : k) + (1 : k)) is not approximatable by (((1 : k)) + ((1 : k))) * c for type k
 
 Counter-example:
-  c = 0 :: k
+  c = 3 :: k