fix: clean comments in text in getDiagramFromText API so flowchart works well

demos/flowchart.html

@@ -1539,7 +1539,11 @@
       class I bugged_node
     </pre>
     <hr />
-
+    <pre class="mermaid">
+      flowchart LR
+  %% this is a comment A -- text --> B{node}
+  A -- text --> B -- text2 --> C
+    </pre>
     <h1 id="link-clicked">Anchor for "link-clicked" test</h1>
 
     <script type="module">