The reasons for making this change are:
- There's no UI available to toggle the cursor-tools in the GeckoView-specific viewer.
- The `HandTool`-implementation basically *simulates* touch scrolling, and is thus unlikely to be helpful/useful anyway.
- PR 15831 already changed the relevant call-sites to handle `PDFViewerApplication.pdfCursorTools` being undefined.
These `@media` rules were most likely just copy-pasted from the regular viewer, however none of them are currently necessary since the GeckoView-specific viewer doesn't have any toolbars.
Note that the whole purpose of these CSS rules are to make the toolbar, of the regular viewer, responsive. If we in the future add toolbars for the GeckoView-specific viewer, these rules most likely wouldn't be usable as-is anyway.
