And since it's relatively unlikely to be used, just leave it
behind a environment variable for now.
[ChangeLog][QtNetwork][Potentially Source-Incompatible] Support for
clear-text http/2 was disabled due to incompatibility with certain
servers. If you were relying on this feature you must re-enable it by
setting the QT_NETWORK_ALLOW_H2C environment variable. For a later
version of Qt it will get a dedicated attribute.
Pick-to: 6.2
Task-number: QTBUG-98642
Change-Id: Id3e360726e285b3128e3e3f4bce9440404c9ad6e
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Maximilian Goldstein <max.goldstein@qt.io>
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
4c930e9d13