--enable-ext-mariadb-connector was removed

...in 26b40fcf "Moving mysqlc into connectivity
as a library", apparently without replacement

Change-Id: Ia1d32f98bd90efe2fcd4441dd84cd1862a4daa70

distro-configs/Jenkins/Linux_ubsan_master.conf

@@ -7,7 +7,6 @@
 --enable-evolution2
 --enable-ext-ct2n
 --enable-ext-languagetool
---enable-ext-mariadb-connector
 --with-system-mariadb
 --enable-ext-nlpsolver
 --enable-ext-numbertext