Revert adding curly braces when migrating env vars in .env files

We do not want curly braces to end in the `.env` file

Author: edif2008

internals/secrethub/migrate_config_envfile.go

@@ -39,7 +39,7 @@ func (cmd *MigrateConfigEnvfileCommand) Run() error {
 		return err
 	}
 
-	output, replaceCount, err := migrateTemplateTags(string(inFileContents), refMapping, "{{ %s }}")
+	output, replaceCount, err := migrateTemplateTags(string(inFileContents), refMapping, "%s")
 	if err != nil {
 		return err
 	}