Remove unnecessary checks that error log functions are in pg_proc.

Long time ago, they apparently weren't in the catalogs, but they're not
going to suddenly disappear from there now, any more than any other
function. The functions themselves are called elsewhere in the test file,
so if they are missing or broken, the test will fail that way.

src/test/regress/input/external_table.source

@@ -310,12 +310,6 @@ select * from tableless_ext;
 SELECT gp_truncate_error_log('*.*');
 SELECT relname, linenum, errmsg FROM gp_read_error_log('tableless_ext');
 
--- Verify that the error log functions are a part of the catalog
--- Earlier these functions were hidden from the catalog and would not show up
--- in pg_proc
-SELECT * from pg_proc where proname = 'gp_read_error_log';
-SELECT * from pg_proc where proname = 'gp_truncate_error_log';
-
 -- Test for error log functionality 
 
 -- Scan with no errors

src/test/regress/output/external_table.source

@@ -579,21 +579,6 @@ SELECT relname, linenum, errmsg FROM gp_read_error_log('tableless_ext');
 ---------+---------+--------
 (0 rows)
 
--- Verify that the error log functions are a part of the catalog
--- Earlier these functions were hidden from the catalog and would not show up
--- in pg_proc
-SELECT * from pg_proc where proname = 'gp_read_error_log';
-      proname      | pronamespace | proowner | prolang | procost | prorows | provariadic | proisagg | prosecdef | proisstrict | proretset | provolatile | pronargs | pronargdefaults | prorettype | proiswin | proargtypes |         proallargtypes         |     proargmodes     |                                 proargnames                                 | proargdefaults |      prosrc       | probin | proconfig | proacl | prodataaccess 
--------------------+--------------+----------+---------+---------+---------+-------------+----------+-----------+-------------+-----------+-------------+----------+-----------------+------------+----------+-------------+--------------------------------+---------------------+-----------------------------------------------------------------------------+----------------+-------------------+--------+-----------+--------+---------------
- gp_read_error_log |           11 |       10 |      12 |       1 |    1000 |           0 | f        | f         | t           | t         | v           |        1 |               0 |       2249 | f        | 25          | {25,1184,25,25,23,23,25,25,17} | {i,o,o,o,o,o,o,o,o} | {exttable,cmdtime,relname,filename,linenum,bytenum,errmsg,rawdata,rawbytes} |                | gp_read_error_log |        |           |        | s
-(1 row)
-
-SELECT * from pg_proc where proname = 'gp_truncate_error_log';
-        proname        | pronamespace | proowner | prolang | procost | prorows | provariadic | proisagg | prosecdef | proisstrict | proretset | provolatile | pronargs | pronargdefaults | prorettype | proiswin | proargtypes | proallargtypes | proargmodes | proargnames | proargdefaults |        prosrc         | probin | proconfig | proacl | prodataaccess 
------------------------+--------------+----------+---------+---------+---------+-------------+----------+-----------+-------------+-----------+-------------+----------+-----------------+------------+----------+-------------+----------------+-------------+-------------+----------------+-----------------------+--------+-----------+--------+---------------
- gp_truncate_error_log |           11 |       10 |      12 |       1 |       0 |           0 | f        | f         | t           | f         | v           |        1 |               0 |         16 | f        | 25          |                |             |             |                | gp_truncate_error_log |        |           |        | m
-(1 row)
-
 -- Test for error log functionality 
 -- Scan with no errors
 CREATE EXTERNAL TABLE exttab_basic_1( i int, j text )