Update Mermaid version to 10.6.0 to get support for multi part generics in class diagrams

[ebjornset]

Mermaid v 10.6.0 supports multi part generics in class diagrams, e.g.

classDiagram
  class Foo {
    +Bar(Func~string,bool~ builder, CancellationToken cancellationToken) Task~string~
  }

While this renders fine in Mermaid v 10.6.0 Online editor, rendering it in VS Code with the current plugin version (2.0.143) fails with "a bomb picture" and the error message

Syntax error in text
mermaid version 10.4.0

[mjbvz]

Fixed by #228