Migrate Open Saas to 0.18.0 (#500)

Author: sodic

.github/workflows/e2e-tests.yml

@@ -10,7 +10,7 @@ on:
 
 env:
   WASP_TELEMETRY_DISABLE: 1
-  WASP_VERSION: 0.17.0
+  WASP_VERSION: 0.18.0
 
 jobs:
   test:

opensaas-sh/app_diff/main.wasp.diff

@@ -1,7 +1,7 @@
 --- template/app/main.wasp
 +++ opensaas-sh/app/main.wasp
 @@ -3,31 +3,32 @@
-     version: "^0.17.0"
+     version: "^0.18.0"
    },
 
 -  title: "My Open SaaS App",