Correct some uses of e.g. and i.e. in message strings and documentation

E.g. means "for example" and i.e. means "that is". Fix a couple uses
that don't match the intended meaning.

Kyotaro Horiguchi

Reviewed by Junwang Zhao and Aleksander Alekseev, with one addition by me
Discussion: https://www.postgresql.org/message-id/flat/20220713.180943.589079824955875739.horikyota.ntt%40gmail.com

doc/src/sgml/ecpg.sgml

@@ -8312,7 +8312,7 @@ EXEC SQL CLOSE DATABASE;
       <term><literal>FREE cursor_name</literal></term>
       <listitem>
        <para>
-        Due to the differences how ECPG works compared to Informix's ESQL/C (i.e., which steps
+        Due to differences in how ECPG works compared to Informix's ESQL/C (namely, which steps
         are purely grammar transformations and which steps rely on the underlying run-time library)
         there is no <literal>FREE cursor_name</literal> statement in ECPG. This is because in ECPG,
         <literal>DECLARE CURSOR</literal> doesn't translate to a function call into

src/bin/pg_upgrade/check.c

@@ -540,7 +540,7 @@ create_script_for_old_cluster_deletion(char **deletion_script_file_name)
 	if (path_is_prefix_of_path(old_cluster_pgdata, new_cluster_pgdata))
 	{
 		pg_log(PG_WARNING,
-			   "\nWARNING:  new data directory should not be inside the old data directory, e.g. %s", old_cluster_pgdata);
+			   "\nWARNING:  new data directory should not be inside the old data directory, i.e. %s", old_cluster_pgdata);
 
 		/* Unlink file in case it is left over from a previous run. */
 		unlink(*deletion_script_file_name);
@@ -564,7 +564,7 @@ create_script_for_old_cluster_deletion(char **deletion_script_file_name)
 		{
 			/* reproduce warning from CREATE TABLESPACE that is in the log */
 			pg_log(PG_WARNING,
-				   "\nWARNING:  user-defined tablespace locations should not be inside the data directory, e.g. %s", old_tablespace_dir);
+				   "\nWARNING:  user-defined tablespace locations should not be inside the data directory, i.e. %s", old_tablespace_dir);
 
 			/* Unlink file in case it is left over from a previous run. */
 			unlink(*deletion_script_file_name);