test: investigate deltachat 2.50 ci regressions

[ccclxxiii]

summary

this updates the bundled relay_minitest test setup to remove usage of the unsupported deltachat config key:

account.set_config("delete_server_after", "10")

deltachat rpc/server 2.50.0 now rejects this key with:

unknown key "delete_server_after": matching variant not found

which causes test-mini account setup to fail before the actual relay tests run.

the same obsolete config also exists in the upstream chatmail/relay cmdeploy test suite, where it causes similar failures during test-cmdeploy runs.

this change only addresses the cmlxc side (src/relay_minitest/support.py) so that the bundled minitest suite remains compatible with deltachat 2.50.0 while upstream relay-side fixes are handled separately.

notes

• the original purpose of delete_server_after is currently unclear
• deltachat core maintainers indicated the setting is no longer supported
• this pr intentionally removes the unsupported config instead of attempting to replace it with another behavior-changing setting
• further relay-side investigation is still ongoing for test_hide_senders_ip_address

ci status

this pr may still show failing ci because test-cmdeploy uses the upstream chatmail/relay cmdeploy test suite, which has its own copy of the same unsupported config in cmdeploy/src/cmdeploy/tests/plugin.py.

that failure is outside the cmlxc source tree and needs a matching relay-side change. the intended validation for this pr is that the bundled test-mini path no longer fails from src/relay_minitest/support.py.

[missytake]

Sounds like the likely culprit.

[link2xt]

Does this work? Now messages will be deleted immediately.

[link2xt]

I would rather pin the core first and then figure out what the problem is.