Formatter breaks BQ named arguments

[kadu-vido]

Some functions in BQ take named arguments, using the syntax argument => value.

Dataform formatter currently adds a space after the = character, causing an error.

Sample query for MRE:

SELECT ST_GEOGFROMGEOJSON('{"type":"Point","coordinates":[0,0]}', make_valid => TRUE)

[BenBirt]

Fixed in #1490.