title: replacing text in Powershell every alternate match
body: <p>I have looked at <a href="https://stackoverflow.com/questions/40162913/replacing-a-block-of-text-in-powershell">this question</a>, and it's close to what I need to do, but the text I need to replace is inconsistent.</p>
  
  <p>I need to replace <code>"`r`n</code> with <code>"</code>, but only the first of the 2 adjacent lines</p>
  
  <p>example: (the full file is 50k lines and up to 500 chars wide)</p>
  
  <pre>
      ID,Name,LinkedRecords
      54429,Abe,
      54247,Jonathan,"
      63460|63461"
      54249,Teresa,
      54418,Cody,
      58046,Joseph,
      58243,David,
      ,Barry,"
      74330"
      C8876,Simon,
      X_10934,David,
  </pre>
  
  <p>should become</p>
  
  <pre>
      ID,Name,LinkedRecords
      54429,Abe,
      54247,Jonathan,"63460|63461"
      54249,Teresa,
      54418,Cody,
      58046,Joseph,
      58243,David,
      ,Barry,"74330"
      C8876,Simon,
      X_10934,David,
  </pre>
  
  <p>I can see <a href="https://stackoverflow.com/questions/40089631/replacing-only-the-first-occurrence-of-a-word-in-a-string">this</a> will probably be useful, but I'm having a hard time getting the command to work as desired</p>