Note that similarity search in MroongaFullText search key does not give good results with TokenBigramSplitSymbolAlpha parser.

also remove mostly duplicate definition of content_translation_title scriptable key.

to avoid possible 'ignore keywords that exist in more than 50% of rows' trap in MySQL FTS.

that now happens with multiple relation dialog with title.

otherwise full text index is used where keywords that appear in more than 50% of rows are ignored.

so that it supports other comparison operators like '>', 'like' etc.