Removed CSS rule hiding the walkthrough button for small devices as i…

[jqi26]

…t has fixed itself.

Proposed changes

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Readded the walkthrough for mobile devices. Addresses issue #1455.
Tested on:

• Chrome ver. 96.0.4664.45
• Firefox ver. 94.0.2
• Edge ver. 96.0.1054.34
• Opera ver. 81.0.4196.60

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