title: drop last column of a dataframe using spark-scala
body: <p>i have a dataframe without header name. I want to drop last column records but without passing column name .
  Is there any way of doing this?</p>
  
  <pre><code>df.drop("colname")
  </code></pre>
  
  <p>instead of passing column name here how can i drop last column from the dataframe.</p>