fix(channels): the Length column shows the sum alone

The "+N without length" line did not fit the 4.5 rem column (88 px of
text in a 56 px cell) and spilled into Tags. The owner wants no such
line there: the cell shows the summed hours, and the channel list no
longer sends a count nothing reads. A playlist's total keeps it.

frontend/src/lib/api/channels.ts

@@ -76,9 +76,8 @@ export interface ManagedChannel {
   /** When the follow reached this list: the subscription import that first saw it, or a
    *  subscribe made here. */
   added_at: string;
+  /** The lengths it knows; a video with none (a live one, a 24/7 archive) is left out. */
   total_duration_seconds: number;
-  /** Live videos the total cannot hold (no length): the "+N without length" beside it. */
-  live_without_length: number;
   priority: number;
   hidden: boolean;
   deep_requested: boolean;