Rollup merge of #143566 - jieyouxu:fix-x86_64-unknown-netbsd, r=fee1-dead

Fix `x86_64-unknown-netbsd` platform support page

`x86_64-unknown-netbsd` is Tier 2 with host tools, not Tier 3.

cc `@he32.`

r? compiler

Author: matthiaskrgr