fix(updater): dead link (#1408)

* docs: broken link in README.md (fixes #1310) (#1311)

* docs: remove appimage link in readme #1082 (#1171)

* Updating Readme according to #1082

Updating Readme according to #1082

* Added explanation

The explanation is now given and the expression is more formal and explanatory, instead of just linking the issue.

* Update use_update_checker.dart

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Co-authored-by: MerkomassDev <70111455+MerkomassDev@users.noreply.github.com>
Co-authored-by: Karim <37943746+ksaadDE@users.noreply.github.com>
Co-authored-by: Kingkor Roy Tirtho <krtirtho@gmail.com>