chore: remove InsertWorkspaceAgentStat query (#12869)

* chore: remove InsertWorkspaceAgentStat query

InsertWorkspaceAgentStats (batch) exists. We only used the singular in
a single unit test place. Removing the single for the batch, reducing
the interface size.

coderd/database/queries/workspaceagentstats.sql

@@ -1,27 +1,3 @@
--- name: InsertWorkspaceAgentStat :one
-INSERT INTO
-	workspace_agent_stats (
-		id,
-		created_at,
-		user_id,
-		workspace_id,
-		template_id,
-		agent_id,
-		connections_by_proto,
-		connection_count,
-		rx_packets,
-		rx_bytes,
-		tx_packets,
-		tx_bytes,
-		session_count_vscode,
-		session_count_jetbrains,
-		session_count_reconnecting_pty,
-		session_count_ssh,
-		connection_median_latency_ms
-	)
-VALUES
-	($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17) RETURNING *;
-
 -- name: InsertWorkspaceAgentStats :exec
 INSERT INTO
 	workspace_agent_stats (