fix: remove accidental assets submodule from repo root

A TrustWallet assets fork got cloned into the repo root during
the submission prep. The clone was moved out to ../trustwallet-assets;
this commit drops the stray submodule reference from git.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: UltraDAGcom

assets

@@ -30,10 +30,10 @@ mkdir -p blockchains/arbitrum/assets/0x9cFD2011DF13d9E394B5Bb59f0f7e7A5C512155b
 
 ```bash
 # From the UltraDAG repo:
-cp /path/to/ultradag/bridge/token-launch-kit/trustwallet/logo.png \
+cp /Users/johan/Projects/15_UltraDAG/bridge/token-launch-kit/trustwallet/logo.png \
    blockchains/arbitrum/assets/0x9cFD2011DF13d9E394B5Bb59f0f7e7A5C512155b/
 
-cp /path/to/ultradag/bridge/token-launch-kit/trustwallet/info.json \
+cp /Users/johan/Projects/15_UltraDAG/bridge/token-launch-kit/trustwallet/info.json \
    blockchains/arbitrum/assets/0x9cFD2011DF13d9E394B5Bb59f0f7e7A5C512155b/
 ```