Test update.
* jk/httpd-test-updates:
t/lib-httpd: increase ssl key size to 2048 bits
t/lib-httpd: drop SSLMutex config
t/lib-httpd: bump required apache version to 2.4
t/lib-httpd: bump required apache version to 2.2
This is a backport onto the `maint-2.39` branch, to improve the CI
health of that branch.
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>