fix: resolve fuzz test failure in testGetBalance_WhenCollectedOverThawing (#1268)

Replace vm.assume with bounded inputs to fix "vm.assume rejected too many inputs" error.
The previous implementation used overly restrictive constraints that caused the fuzzer
to reject most random inputs. Now limits amountThawing and amountCollected to half of
MAX_STAKING_TOKENS, guaranteeing valid deposit ranges while maintaining test coverage.

Author: RembrandtK

packages/horizon/test/unit/escrow/getters.t.sol

@@ -35,20 +35,17 @@ contract GraphEscrowGettersTest is GraphEscrowTest {
         uint256 amountThawing,
         uint256 amountCollected
     ) public useGateway {
-        amountThawing = bound(amountThawing, 1, MAX_STAKING_TOKENS);
-        amountCollected = bound(amountCollected, 1, MAX_STAKING_TOKENS);
+        // Limit thawing and collected to half of MAX_STAKING_TOKENS to ensure valid deposit range
+        amountThawing = bound(amountThawing, 1, MAX_STAKING_TOKENS / 2);
+        amountCollected = bound(amountCollected, 1, MAX_STAKING_TOKENS / 2);
 
         // amountDeposit must be:
         // - >= amountThawing (so we can thaw that amount)
         // - >= amountCollected (so we can collect that amount)
         // - < amountThawing + amountCollected (so that after collecting, balance < thawing)
-        // - <= MAX_STAKING_TOKENS (consistent with other tests)
+        // With the above bounds, this range is guaranteed to be valid
         uint256 minDeposit = amountThawing > amountCollected ? amountThawing : amountCollected;
         uint256 maxDeposit = amountThawing + amountCollected - 1;
-        if (maxDeposit > MAX_STAKING_TOKENS) {
-            maxDeposit = MAX_STAKING_TOKENS;
-        }
-        vm.assume(minDeposit <= maxDeposit);
         amountDeposit = bound(amountDeposit, minDeposit, maxDeposit);
 
         _depositTokens(users.verifier, users.indexer, amountDeposit);