MDEV-27033: Clean lintian 'duplicate-override-context' warnings

Fix Debian lintian warnings:
  W: mariadb-10.7 source: duplicate-override-context version-substvar-for-external-package (lines 12 13) [debian/source/lintian-overrides:13]
  W: mariadb-10.7 source: duplicate-override-context version-substvar-for-external-package (lines 14 15) [debian/source/lintian-overrides:15]
  W: mariadb-10.7 source: duplicate-override-context version-substvar-for-external-package (lines 16 17) [debian/source/lintian-overrides:17]
  W: mariadb-10.7 source: duplicate-override-context version-substvar-for-external-package (lines 18 19) [debian/source/lintian-overrides:19]
  W: mariadb-10.7 source: duplicate-override-context version-substvar-for-external-package (lines 20 21) [debian/source/lintian-overrides:21]
  W: mariadb-10.7 source: duplicate-override-context version-substvar-for-external-package (lines 4 5) [debian/source/lintian-overrides:5]
by removing duplicate override lines

debian/source/lintian-overrides

@@ -2,7 +2,6 @@
 # since package breaks/replaces these but at the same time also provides them
 version-substvar-for-external-package mariadb-client-core-10.7 -> mysql-client-5.5
 version-substvar-for-external-package mariadb-server-10.7 -> mysql-server
-version-substvar-for-external-package mariadb-server-10.7 -> mysql-server
 version-substvar-for-external-package libmariadb-dev -> libmysqlclient-dev
 version-substvar-for-external-package libmariadb-dev -> libmysqld-dev
 version-substvar-for-external-package mariadb-server-10.7 -> mysql-client-5.5
@@ -10,15 +9,10 @@ version-substvar-for-external-package mariadb-server-10.7 -> mysql-client-5.6
 version-substvar-for-external-package mariadb-server-10.7 -> mysql-client-5.7
 version-substvar-for-external-package mariadb-server-10.7 -> mysql-client-8.0
 version-substvar-for-external-package mariadb-client-10.7 -> mysql-client-core-5.1
-version-substvar-for-external-package mariadb-client-10.7 -> mysql-client-core-5.1
-version-substvar-for-external-package mariadb-client-10.7 -> mysql-client-core-5.5
 version-substvar-for-external-package mariadb-client-10.7 -> mysql-client-core-5.5
 version-substvar-for-external-package mariadb-client-10.7 -> mysql-client-core-5.6
-version-substvar-for-external-package mariadb-client-10.7 -> mysql-client-core-5.6
-version-substvar-for-external-package mariadb-client-10.7 -> mysql-client-core-5.7
 version-substvar-for-external-package mariadb-client-10.7 -> mysql-client-core-5.7
 version-substvar-for-external-package mariadb-client-10.7 -> mysql-client-core-8.0
-version-substvar-for-external-package mariadb-client-10.7 -> mysql-client-core-8.0
 version-substvar-for-external-package libmariadbd-dev -> libmariadbclient-dev
 # ColumnStore not used in Debian, safe to ignore. Reported upstream in https://jira.mariadb.org/browse/MDEV-24124
 source-is-missing storage/columnstore/columnstore/utils/jemalloc/libjemalloc.so.2