fix(nav): drop the wrong asset from the Stake menu description (#256)

The description said "Back a Gnars rider with MOR" / "com MOR". The default
path in the rider dialog is `vault-usdc` — a USDC deposit into the rider's
Morpho vault on Base. MOR is the asset of the *other* layer, the Gnars Builder
subnet, which is a different product with a different promise (there you keep
none of the yield).

I introduced this in 4a809f2 by carrying "with MOR" over from the subnet copy,
and it shipped. With the rider campaign now saying "deposit USDC on Base", the
menu was contradicting both the page and the campaign.

Names no asset at all, matching the page's own hero ("Back a Gnars rider. Your
deposit stays yours and keeps earning."). Naming one would be the same mistake
in the other direction: the dialog offers three — USDC into the Morpho vault,
and stETH or USDC into Morpheus Capital.

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

Author: sktbrd

messages/en/nav.json

@@ -39,7 +39,7 @@
       },
       "stake": {
         "title": "Stake",
-        "description": "Back a Gnars rider with MOR — your deposit stays yours and keeps earning"
+        "description": "Back a Gnars rider — your deposit stays yours and keeps earning"
       },
       "rounds": {
         "title": "Rounds",

messages/pt-br/nav.json

@@ -39,7 +39,7 @@
       },
       "stake": {
         "title": "Stake",
-        "description": "Apoie um rider da Gnars com MOR — seu depósito continua seu e rendendo"
+        "description": "Apoie um rider da Gnars — seu depósito continua seu e rendendo"
       },
       "rounds": {
         "title": "Rounds",