chore(stake): drop four unused MOR strings (#259)

`opp.youKeepMor`, `opp.donateOpt`, `opp.morHow` and `opp.athleteBonus` are not
referenced anywhere in the codebase — leftovers from an opt-in model the code
never implemented.

They were also actively misleading. "You keep 100% of the MOR" and "Optionally
donate your MOR to the split" describe a flow where the split is a choice the
staker makes. What `use-morpheus-stake.ts` actually does is wire the claim
receiver to the 3-way split (staker 50 / Gnars 25 / athlete 25) by default,
right after the deposit, as a second signature. Keeping 100% is the exception —
it happens only if that second prompt is declined — and there is no UI for it.
`lootbox.hint` ("You keep 50% · Gnars 25% · athlete 25%") is the one the user
actually sees, and it is correct.

Deleting rather than rewriting: making them accurate would mean describing a
toggle that does not exist. The opt-out is a product decision, not a copy fix.

Both locales, 283 keys each, identical order. Verified the dialog's 20 live
`opp.*` keys all still resolve.

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

Author: sktbrd

messages/en/stake.json

@@ -118,10 +118,6 @@
     "morUsdc": "Morpheus USDC",
     "estNote": "≈{rate}% APR estimate — swings with the MOR price and pool size.",
     "mainnetWarn": "Ethereum mainnet — real gas. Principal unlocks after a 7-day lock.",
-    "morHow": "How the MOR flows",
-    "youKeepMor": "You keep 100% of the MOR",
-    "athleteBonus": "{name} earns a referrer bonus (protocol-funded)",
-    "donateOpt": "Optionally donate your MOR to the split",
     "estYearLabel": "Estimated value / year",
     "estYearNote": "Paid in MOR on Arbitrum — a live estimate, not a guarantee.",
     "approving": "approving…",

messages/pt-br/stake.json

@@ -118,10 +118,6 @@
     "morUsdc": "Morpheus USDC",
     "estNote": "≈{rate}% APR estimado — varia com o preço do MOR e o tamanho do pool.",
     "mainnetWarn": "Ethereum mainnet — gas real. O principal destrava após um lock de 7 dias.",
-    "morHow": "Como o MOR flui",
-    "youKeepMor": "Você fica com 100% do MOR",
-    "athleteBonus": "{name} ganha um bônus de indicação (pago pelo protocolo)",
-    "donateOpt": "Opcional: doe seu MOR pro split",
     "estYearLabel": "Valor estimado / ano",
     "estYearNote": "Pago em MOR na Arbitrum — estimativa ao vivo, não é garantia.",
     "approving": "aprovando…",