Merge "docs: Fixed Marshmallow links in API level table." into mnc-mr-docs

<table>

  <tr><th>Platform Version</th><th>API Level</th><th>VERSION_CODE</th><th>Notes</th></tr>

    <tr><td>Android 6.0</td>

    <tr><td><a href="{@docRoot}about/versions/marshmallow/android-6.0.html">Android 6.0</a></td>

    <td><a href="{@docRoot}sdk/api_diff/23/changes.html" title="Diff Report">23</a></td>

    <td>{@link android.os.Build.VERSION_CODES#M}</td>

    <td><a href="{@docRoot}preview/api-overview.html">API Changes</a></td></tr>

    <td><a href="{@docRoot}about/versions/marshmallow/index.html">Platform Highlights</a></td></tr>

    <tr><td><a href="{@docRoot}about/versions/android-5.1.html">Android 5.1</a></td>

    <td><a href="{@docRoot}sdk/api_diff/22/changes.html" title="Diff Report">22</a></td>