Revert "Allow complex values in variables parameter of terraform module (#4281)" (#4368)

This reverts commit 4cc7f41395.

plugins/modules/cloud/misc/terraform.py

@@ -443,7 +443,7 @@ def main():
     for k, v in variables.items():
         variables_args.extend([
             '-var',
-            '{0}={1}'.format(k, json.dumps(v))
+            '{0}={1}'.format(k, v)
         ])
     if variables_files:
         for f in variables_files: