Round off random_normal() test results one more decimal place.

As I suspected, some machines have even more low-order-bit
inaccuracy than the ones I tested.  Tweak new test so that
(hopefully) it will pass everywhere.  Per buildfarm.

Discussion: https://postgr.es/m/4173840.1673290336@sss.pgh.pa.us

src/test/regress/expected/random.out

@@ -113,34 +113,34 @@ SELECT random() FROM generate_series(1, 10);
 -- Likewise for random_normal(); however, since its implementation relies
 -- on libm functions that have different roundoff behaviors on different
 -- machines, we have to round off the results a bit to get consistent output.
-SET extra_float_digits = 0;
+SET extra_float_digits = -1;
 SELECT random_normal() FROM generate_series(1, 10);
    random_normal   
---------------------
+-------------------
-  0.208534644938377
+  0.20853464493838
-  0.264530240540963
+  0.26453024054096
- -0.606752467900428
+ -0.60675246790043
-  0.825799427852654
+  0.82579942785265
-   1.70111611735357
+   1.7011161173536
- -0.223445463716189
+ -0.22344546371619
-  0.249712419190998
+    0.249712419191
   -1.2494722990669
-  0.125627152043677
+  0.12562715204368
-  0.475391614544013
+  0.47539161454401
 (10 rows)
 
 SELECT random_normal(mean => 1, stddev => 0.1) r FROM generate_series(1, 10);
         r         
--------------------
+------------------
-  1.00605972811732
+  1.0060597281173
-  1.09685453015002
+    1.09685453015
-  1.02869206132007
+  1.0286920613201
- 0.909475676712336
+ 0.90947567671234
- 0.983724763134265
+ 0.98372476313426
- 0.939344549577623
+ 0.93934454957762
-  1.18713500206363
+  1.1871350020636
- 0.962257684292933
+ 0.96225768429293
- 0.914441206800407
+ 0.91444120680041
- 0.964031055575433
+ 0.96403105557543
 (10 rows)
 

src/test/regress/sql/random.sql

@@ -79,7 +79,7 @@ SELECT random() FROM generate_series(1, 10);
 -- Likewise for random_normal(); however, since its implementation relies
 -- on libm functions that have different roundoff behaviors on different
 -- machines, we have to round off the results a bit to get consistent output.
-SET extra_float_digits = 0;
+SET extra_float_digits = -1;
 
 SELECT random_normal() FROM generate_series(1, 10);
 SELECT random_normal(mean => 1, stddev => 0.1) r FROM generate_series(1, 10);