docs: edit description of some metrics

Author: casperr0

README.rst

@@ -235,10 +235,10 @@ Metrics:  PostgreSQL
     'PostgreSQL: number of idle connections': pgsql.connections[fastpath_function_call]
     'PostgreSQL: number of idle connections': pgsql.connections[disabled]
     'PostgreSQL: number of idle connections': pgsql.connections[max_connections]
-    'PostgreSQL: count files in archive_status need to archive pgsql.archive_command[count_files_to_archive]
-    'PostgreSQL: size of files need to archive pgsql.archive_command[size_files_to_archive]
-    'PostgreSQL: count archived files pgsql.archive_command[archived_files]
-    'PostgreSQL: count attempts to archive files pgsql.archive_command[failed_trying_to_archive]
+    'PostgreSQL: count files in archive_status need to archive': pgsql.archive_command[count_files_to_archive]
+    'PostgreSQL: size of files need to archive': pgsql.archive_command[size_files_to_archive]
+    'PostgreSQL: count archived files': pgsql.archive_command[archived_files]
+    'PostgreSQL: count attempts to archive files': pgsql.archive_command[failed_trying_to_archive]
     'PostgreSQL checkpoint: by timeout (in hour)': pgsql.checkpoint[count_timed]
     'PostgreSQL checkpoint: by wal (in hour)': pgsql.checkpoint[count_wal]
     'PostgreSQL checkpoint: write time': pgsql.checkpoint[write_time]