Improving documentation (for jasmine_sprout)

Hey all I noticed a few things installing calyx myself. And I wanted to create a PR to fix these isseus in the documentation. This isseu is for tracking simular/related isseus and linking PR's/commits. If you have noticed anything simular leave a comment, maybe i'll fix it aswell

• The installation documentation links to hhttps://gitlab.com/calyxos/calyxos/-/wikis/mi-a2 which is marked as decpreta on the wiki home page altough it was updated only a week ago.
• In general for the MI A2 I wanted to update the docs. And include some better docs for flashing to the original version, as for me this has proven to be quite troublesome
• Add information about the warning about having a unlocked bootloader that only seems to appear when the bootloader is in fact locked( flashed my device 3 times over before I figured this one out), this was discussed in another issue if someone could link it i would appreciate it as I plan to include it on the docs.