Deb: Rename mariadb.init 10.5->10.6 on 10.6 branch

Also fix a few other occurences of 10.5 -> 10.6.

This commit complements commit 4501c7e875
that seem to have missed these changes.

debian/mariadb-server-10.6.config

@@ -9,6 +9,6 @@ ${DEBIAN_SCRIPT_TRACE:+ echo "#42#DEBUG# RUNNING $0 $*" 1>&2 }
 
 # Beware that there are two ypwhich one of them needs the 2>/dev/null!
 if test -n "`which ypwhich 2>/dev/null`"  &&  ypwhich >/dev/null 2>&1; then
-  db_input high mariadb-server-10.5/nis_warning || true
+  db_input high mariadb-server-10.6/nis_warning || true
   db_go
 fi

debian/salsa-ci.yml

@@ -625,7 +625,7 @@ mysql-8.0 Focal to mariadb-10.6 upgrade:
   # Installation often fails (not a MariaDB reason), so do not require this test to pass
   allow_failure: true
 
-mysql-5.7 Bionic to mariadb-10.5 upgrade:
+mysql-5.7 Bionic to mariadb-10.6 upgrade:
   stage: upgrade extras
   needs:
     - job: build stretch-backports