title: I set 'truncation=True' when using Tapas Tokenizer in transformers, but still get a warning of not setting truncation explicitly
body: <p>The warning is:</p>
  <blockquote>
  <p>Truncation was not explicitly activated but <code>max_length</code> is provided
  a specific value, please use <code>truncation=True</code> to explicitly truncate
  examples to max length. Defaulting to 'longest_first' truncation
  strategy. If you encode pairs of sequences (GLUE-style) with the
  tokenizer you can select this strategy more precisely by providing a specific strategy to <code>truncation</code>.</p>
  </blockquote>
  <p>and my code is</p>
  <pre><code>tokenizer = AutoTokenizer.from_pretrained(&quot;google/tapas-base&quot;)
  item = tokenizer(table = table, queries = queries, max_length = 256, truncation=True)
  </code></pre>
  <p>The version of my transformers 4.15.0. I really wonder what the problem is.</p>