[TASK] Amend Installer text

This commit is intended to improve the language
used in the Installer.

[+] Review each paragraph and amend if required
[+] Consistent buttons names

[-] Remove unnecessary text that is not relevant
to the installation process.

Resolves: #84839
Releases: master

Change-Id: I1288f3942214cc2687b8e5ef0d51f678f2d5bc23
Reviewed-on: https://review.typo3.org/56783


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Tested-by: Tymoteusz Motylewski <t.motylewski@gmail.com>