removed all but one extension, so we can focus on core

lnbits/extensions/example/migrations.py

@@ -1,10 +0,0 @@
-# async def m001_initial(db):
-#    await db.execute(
-#        f"""
-#        CREATE TABLE example.example (
-#            id TEXT PRIMARY KEY,
-#            wallet TEXT NOT NULL,
-#            time TIMESTAMP NOT NULL DEFAULT {db.timestamp_now}
-#        );
-#    """
-#    )