bin/duckpan - Fixed some spelling mistakes in help

**Which issues (if any) does this change solve? (please link them here)**

There are a few minor spelling mistakes present in the duckpan help display. I have corrected them and I am now submitting a pull request for this to be merged.

**Briefly describe your fix. Are there any important details we should know about?**

Fixing the spelling mistakes present. Nothing else to know :)

**Are you having any problems? Do you need our help with anything?**

Everything is fine!

**Where did you hear about DuckDuckHack? (For first time contributors)**

Through DuckDuckGo. I am a developer so I wanted to see how I can contribute.