update tests to expect success for all 2.7.15 builds

test/run

@@ -81,20 +81,12 @@ testPylibmc() {
 }
 
 testPython2() {
-  if [[ "$STACK" == "heroku-16" ]] || [[ "$STACK" == "cedar-14" ]]; then
     compile "python2"
     assertCaptured "python-2.7.15"
     assertCapturedSuccess
   fi
 }
 
-testNoPython2() {
-  if [[ "$STACK" == "heroku-18" ]]; then
-    compile "python2"
-    assertCapturedError
-  fi
-}
-
 testPython3() {
   compile "python3"
   assertCaptured "python-3.6.6"