Merge bitcoin#28014: ci: re-enable gui tests for s390x

Co-authored-by: fanquake <[email protected]>

Author: DashCoreAutoGuix

ci/test/00_setup_env_s390x.sh

@@ -22,4 +22,4 @@ export RUN_UNIT_TESTS=true
 export TEST_RUNNER_EXTRA="--exclude rpc_bind,feature_bind_extra"  # Excluded for now, see https://github.com/bitcoin/bitcoin/issues/17765#issuecomment-602068547
 export RUN_FUNCTIONAL_TESTS=true
 export GOAL="install"
-export BITCOIN_CONFIG="--enable-reduce-exports --disable-gui-tests --with-boost-process"  # GUI tests disabled for now, see https://github.com/bitcoin/bitcoin/issues/23730
+export BITCOIN_CONFIG="--enable-reduce-exports --with-boost-process"