Use construct_array_builtin for FLOAT8OID instead of construct_array.

Commit d746021de1 introduced construct_array_builtin() for built-in
data types, but forgot some replacements linked to FLOAT8OID.

Author: Bertrand Drouvot
Reviewed-by: Peter Eisentraut
Discussion: https://postgr.es/m/CAD21AoCERkwmttY44dqUw%3Dm_9QCctu7W%2Bp6B7w_VqxRJA1Qq_Q%40mail.gmail.com

src/backend/utils/adt/arrayfuncs.c

@@ -3404,6 +3404,12 @@ construct_array_builtin(Datum *elems, int nelems, Oid elmtype)
 			elmalign = TYPALIGN_INT;
 			break;
 
+		case FLOAT8OID:
+			elmlen = sizeof(float8);
+			elmbyval = FLOAT8PASSBYVAL;
+			elmalign = TYPALIGN_DOUBLE;
+			break;
+
 		case INT2OID:
 			elmlen = sizeof(int16);
 			elmbyval = true;