installer: Deprecate WebInstaller::getInfoBox, getWarningBox and getErrorBox
Since MW 1.31 there are messageBox, warningBox, errorBox and successBox
available which should be used instead.
These are simple wrappers around Html::messageBox and related methods
which should be used directly instead. Internal usage has been migrated
as of
a9252abb1cf0, but these public methods remain for now. Once
removed we can also removed the internal Html::infoBox() method.
Bug: T232903
Change-Id: I2756c88987754c4e3f84d98c531d8396098cd7fe