[flights] Remove cast causing Clickhouse error

[trzysiek]

Casting to simple Float is dangerous, as the column can be Nullable(Float), and Clickhouse panics. It's also unnecessary, as we stopped keeping geo as Strings.

Gets rid of

Error processing request: clickhouse: iterating over rows failed:  code: 349, message:
Cannot convert NULL value to non-Nullable type: while executing
'FUNCTION CAST(__table1.geoip_location_lat :: 1, 'Float'_String : 9) -> CAST(__table1.geoip_location_lat, 'Float'_String) Float32 : 12'	

[trzysiek]

/run-integration-tests