shell: Set the 'navigate' icon to the Explore page

This better represent the metaphor of this page.
1 job for librem5-3-34-0
latest
Status Job ID Name Coverage
  Build
failed #293075
build-gnome-software

 
Name Stage Failure
failed
build-gnome-software Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job log