Rollup merge of rust-lang#118712 - davidtwco:targets-remove-i386-i486, r=compiler-errors

targets: remove not-added {i386,i486}-unknown-linux-gnu

These files were added to the repository but never wired up so they could be used - and that was a few years ago without anyone noticing - so let's remove these, they can be re-added if someone wants them.

cc rust-lang#80662
r? ```@pnkfelix``` (familiar with the tier policy and Wesley is on vacation)

Author: matthiaskrgr