fix: trim the direction string in flowchart

.changeset/smart-humans-cover.md

@@ -0,0 +1,5 @@
+---
+'mermaid': patch
+---
+
+fix: Update flowchart direction TD's behavior to be the same as TB

packages/mermaid/src/diagrams/flowchart/flowDb.ts

@@ -403,7 +403,8 @@ You have to call mermaid.initialize.`
    *
    */
   public setDirection(dir: string) {
-    this.direction = dir;
+    this.direction = dir.trim();
+
     if (/.*</.exec(this.direction)) {
       this.direction = 'RL';
     }