docs(compose): trim the ticketEV comment

Keep the rule and one worked number. Why 1e9 was too low belongs in the
commit that raised it, not in the file.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: rickstaa

compose.onchain.yml

@@ -51,11 +51,9 @@ services:
       # Price comes from the app's registration; -pricePerUnit only sets the
       # unused legacy base price, but an on-chain O won't boot without it.
       - -pricePerUnit=0
-      # Expected value per ticket. It sets how many tickets one payment needs
-      # (fee / ticketEV), and the signer refuses to sign more than 100 at once.
-      # A metered session pays for a 10s window upfront, so at 1e9 the ceiling
-      # would be about 0.067 USD per hour, under what echo advertises. 1e10
-      # leaves room: echo's 0.10 per hour signs 15 tickets upfront, 6 per top-up.
+      # Expected value per ticket. A payment needs fee / ticketEV tickets and the
+      # signer signs at most 100 at once, which is what caps the price. At 1e10
+      # echo's 0.10 USD per hour signs 15 tickets upfront, 6 per top-up.
       - -ticketEV=10000000000
       - -maxFaceValue=4000000000000000
       - -monitor=false