Aggs can't use named arguments (github#565)

Remove the named args in the counter_agg as they don't work.

Co-authored-by: Lana Brindley <github@lanabrindley.com>
Co-authored-by: Jacob Prall <prall.jacob@gmail.com>

timescaledb/how-to-guides/hyperfunctions/counter-aggs.md

@@ -88,7 +88,7 @@ going on in each part.
     with t as (
         SELECT measure_id,
             time_bucket('15 min'::interval, ts) as bucket,
-            counter_agg(ts, val, bounds => time_bucket_range('15 min'::interval, ts))
+            counter_agg(ts, val, time_bucket_range('15 min'::interval, ts))
         FROM example
         GROUP BY measure_id, time_bucket('15 min'::interval, ts))
     SELECT time_bucket,
@@ -122,7 +122,7 @@ out of it.
     WITH (timescaledb.continuous)
     AS SELECT measure_id,
         time_bucket('15 min'::interval, ts) as bucket,
-        counter_agg(ts, val, bounds => time_bucket_range('15 min'::interval, ts))
+        counter_agg(ts, val, time_bucket_range('15 min'::interval, ts))
     FROM example
     GROUP BY measure_id, time_bucket('15 min'::interval, ts);
     ```