Increase timeout in statement_timeout test from 1 second to 2 seconds.

We have once or twice seen failures suggesting that control didn't get
to the exception block before the timeout elapsed, which is unlikely
but not impossible in a parallel regression test (with a dozen other
backends competing for cycles).  This change doesn't completely prevent
the problem of course, but it should reduce the probability enough that
we don't see it anymore.  Per buildfarm results.

src/test/regress/expected/plpgsql.out

@@ -1902,7 +1902,7 @@ begin
   begin
     x := x + 1;
     insert into foo values(x);
-    -- we assume this will take longer than 1 second:
+    -- we assume this will take longer than 2 seconds:
     select count(*) into x from tenk1 a, tenk1 b, tenk1 c;
   exception
     when others then
@@ -1915,7 +1915,7 @@ begin
   insert into foo values(x);
   return x;
 end$$ language plpgsql;
-set statement_timeout to 1000;
+set statement_timeout to 2000;
 select blockme();
 NOTICE:  nyeah nyeah, can't stop me
  blockme 

src/test/regress/sql/plpgsql.sql

@@ -1674,7 +1674,7 @@ begin
   begin
     x := x + 1;
     insert into foo values(x);
-    -- we assume this will take longer than 1 second:
+    -- we assume this will take longer than 2 seconds:
     select count(*) into x from tenk1 a, tenk1 b, tenk1 c;
   exception
     when others then
@@ -1688,7 +1688,7 @@ begin
   return x;
 end$$ language plpgsql;
 
-set statement_timeout to 1000;
+set statement_timeout to 2000;
 
 select blockme();