MDEV-23024 Remove Cassandra Storage Engine

Cassandra has long been non-functional, doesn't compile, etc.,
and development on it has halted. Since MariaDB Server 10.5,
the build is disabled by default.

It makes sense to remove it as it's just taking up space.

cmake/build_configurations/mysql_release.cmake

@@ -74,7 +74,6 @@ IF(FEATURE_SET)
   ENDIF()
   IF(num GREATER FEATURE_SET_large)
     SET(PLUGIN_PARTITION "STATIC")
-    #SET(PLUGIN_CASSANDRA "STATIC")
   ENDIF()
   IF(num GREATER FEATURE_SET_xlarge)
    # OPTION(WITH_ALL ON) 

debian/rules

@@ -82,7 +82,6 @@ endif
 	    -DCMAKE_SYSTEM_PROCESSOR=$(DEB_HOST_ARCH) \
 	    -DBUILD_CONFIG=mysql_release \
 	    -DPLUGIN_TOKUDB=NO \
-	    -DPLUGIN_CASSANDRA=NO \
 	    -DPLUGIN_COLUMNSTORE=YES \
 	    -DPLUGIN_ROCKSDB=YES \
 	    -DPLUGIN_AWS_KEY_MANAGEMENT=NO \