Revert r53600 "Add $wgSecondaryGoNamespace, used if an exact match is not found when...

Revert r53600 "Add $wgSecondaryGoNamespace, used if an exact match is not found when pressing go - will try to find a match in a different namespace before performing a search."
Revert r53618 "* Replace $wgSecondaryGoNamespace with $wgSecondaryGoNamespaces (taking an array of integers instead of just an integer), per code review of r53600."
Revert r53672 "* Add release note for r53618."
Per bug 11380 this should probably be using the default search namespaces or the user's search namespaces; an additional config array seems unnecessary.