telecenter.sql: Return collect_{date,time} as a single timestamp

Signed-off-by: Diego Giovane Pasqualin <dpasqualin@c3sl.ufpr.br>

web/queries/tlbr/net_usage/telecenter.sql

 SELECT
-    telecenter
-    , kbits_five_min_to_mbits_sec(down_kbits) AS down_kbits
-    , kbits_five_min_to_mbits_sec(up_kbits) AS up_kbits
-    , CAST(collect_time AS varchar) AS collect_time
-    , CAST(id_date AS varchar) AS id_date
+    telecenter AS cat
+    , kbits_five_min_to_mbits_sec(down_kbits) AS down
+    , kbits_five_min_to_mbits_sec(up_kbits) AS up
+    , collect_date + collect_time AS timestamp
 FROM
     fact_net_usage_telecenter
 WHERE