contrib: add script to demo/test assumeutxo

Add the script to the shellcheck exception list since the
quoted variables rule needs to be violated in order to get
bitcoind to pick up on $CHAIN_HACK_FLAGS.

test/lint/lint-shell.py

@@ -67,9 +67,13 @@ def main():
         '*.sh',
     ]
     files = get_files(files_cmd)
-    # remove everything that doesn't match this regex
     reg = re.compile(r'src/[leveldb,secp256k1,minisketch]')
-    files[:] = [file for file in files if not reg.match(file)]
+
+    def should_exclude(fname: str) -> bool:
+        return bool(reg.match(fname)) or 'test_utxo_snapshots.sh' in fname
+
+    # remove everything that doesn't match this regex
+    files[:] = [file for file in files if not should_exclude(file)]
 
     # build the `shellcheck` command
     shellcheck_cmd = [