Remove sysinfo/linux-netdevs feature

[shouya]

This PR removes the linux-netdevs feature from sysinfo dependency.

Rationale: I recently discovered the issue of non-responding eww resulting from a seemingly unrelated bad nfs mount. From what's stated in the API documentation, enabling linux-netdevs can result in hangs in sysinfo::Disks APIs when there are network mounts.

I found this feature was enabled in #958, in an attempt to fix a EWW_NET display issue. However, despite the naming suggests, sysinfo/linux-netdevs has nothing to do linux network interfaces. As can be seen from this search, the only place linux-netdevs takes effect is to determine whether or not network filesystems are included in the Disks API.

Therefore, I concluded that this feature may be added accidentally.