message: Removed confusing leftNav content from Overview
diff: -### Using iModelJs
  -
  -- [iModelJs Architecture](./SoftwareArchitecture.md)
  -- [Agents and Services](./SoftwareArchitecture.md#web)
  -- [Web Apps](./SoftwareArchitecture.md#web)
  -- [Desktop Apps](./SoftwareArchitecture.md#desktop)
  -- [Mobile Apps](./SoftwareArchitecture.md#mobile)
  -
  -&nbsp;
  -### Helpful Background Information
  -
  -- [iModels](./iModels.md)
  -- [iModelHub](./IModelHub.md)
  -- [iModel Bridges](./imodel-bridges.md)
  -- [BIS Introduction](../bis/index.md)
  -- [Remote Procedure Calls](./RpcInterface.md)
  -- [iModelJs Packages](./index.md#imodeljs-organization)
  -- [Glossary](../learning/glossary.md)
  