pgsql: doc: add float as an alias for double precision.

doc: add float as an alias for double precision.

Although the "Floating-Point Types" section says that "float" data
type is taken to mean "double precision", this information was not
reflected in the data type table that lists all data type aliases.

Reported-by: alexander.kjall@hafslund.no
Author: Euler Taveira <euler@eulerto.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/175456294638.800.12038559679827947313@wrigleys.postgresql.org
Backpatch-through: 13

Branch
------
REL_18_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/31c09ef4563612467b31149713896948e5532684

Modified Files
--------------
doc/src/sgml/datatype.sgml | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)