Remove unused messages in the installer

Remove unused messages in the installer

Removes messages:

config-db-charset
https://github.com/wikimedia/mediawiki/search?utf8=%E2%9C%93&q=config-db-charset&type=Code

config-charset-mysql5-binary
https://github.com/wikimedia/mediawiki/search?utf8=%E2%9C%93&q=config-charset-mysql5-binary&type=Code

config-charset-mysql5
https://github.com/wikimedia/mediawiki/search?utf8=%E2%9C%93&q=config-charset-mysql5&type=Code

config-charset-mysql4
https://github.com/wikimedia/mediawiki/search?utf8=%E2%9C%93&q=config-charset-mysql4&type=Code

config-charset-help
https://github.com/wikimedia/mediawiki/search?utf8=%E2%9C%93&q=config-charset-help&type=Code

Shows them as all being unused.

Plus we doint use mysql 4 any more nor support it.

Change-Id: I369e4f6d3fd934398d978d3fa8c0da6a62bd8a0f