fix: `isRelational` to return a boolean

Previously, `Connector.prototype.isRelational()` returned itself (a
function). This fix ensures that a boolean based on
`Connector.prototype.relational` is returned instead.

Signed-off-by: Rifa Achrinza <25147899+achrinza@users.noreply.github.com>

lib/connector.js

@@ -33,7 +33,7 @@ Connector.prototype.relational = false;
  * @returns {Boolean} true for relational DB
  */
 Connector.prototype.isRelational = function() {
-  return this.isRelational ||
+  return this.relational ||
     (this.getTypes().indexOf('rdbms') !== -1);
 };