Adjust EXPLAIN test case to filter out "Actual Rows" values.

Per the buildfarm, these tests appear to be unstable in the wake of
commit ddb17e387a. I'm not sure that
just hiding this output is the right way forward, because I think
there may be other test cases that will fail with lower probability
even after this fix. However, it's hard to tell right now, because
this is failing on a number of buildfarm animals. So let's try this
for now to either get a clearer picture of what else is broken, or
as a stopgap until we decide what the permanent fix should be, or
perhaps this will be the permanent fix after all.

src/test/regress/expected/explain.out

@@ -493,6 +493,9 @@ select jsonb_pretty(
   -- Also remove its sort-type fields, as those aren't 100% stable
   #- '{0,Plan,Plans,0,Sort Method}'
   #- '{0,Plan,Plans,0,Sort Space Type}'
+  -- Actual Rows can be 0 or 0.0 depending on whether loops>1
+  #- '{0,Plan,Plans,0,Actual Rows}'
+  #- '{0,Plan,Plans,0,Plans,0,Actual Rows}'
 );
                         jsonb_pretty                         
 -------------------------------------------------------------
@@ -528,7 +531,6 @@ select jsonb_pretty(
                              "Plan Rows": 0,                +
                              "Plan Width": 0,               +
                              "Total Cost": 0.0,             +
-                             "Actual Rows": 0.0,            +
                              "Actual Loops": 0,             +
                              "Startup Cost": 0.0,           +
                              "Async Capable": false,        +
@@ -575,7 +577,6 @@ select jsonb_pretty(
                      "Plan Rows": 0,                        +
                      "Plan Width": 0,                       +
                      "Total Cost": 0.0,                     +
-                     "Actual Rows": 0.0,                    +
                      "Actual Loops": 0,                     +
                      "Startup Cost": 0.0,                   +
                      "Async Capable": false,                +

src/test/regress/sql/explain.sql

@@ -147,6 +147,9 @@ select jsonb_pretty(
   -- Also remove its sort-type fields, as those aren't 100% stable
   #- '{0,Plan,Plans,0,Sort Method}'
   #- '{0,Plan,Plans,0,Sort Space Type}'
+  -- Actual Rows can be 0 or 0.0 depending on whether loops>1
+  #- '{0,Plan,Plans,0,Actual Rows}'
+  #- '{0,Plan,Plans,0,Plans,0,Actual Rows}'
 );
 
 rollback;