Relax char limit on Modified table header from 12 to 18.

    <string name="sort_dimension_name">Name</string>

    <!-- Table header for metadata of downloaded files, such as download source and progress. [CHAR_LIMIT=24] -->

    <string name="sort_dimension_summary">Summary</string>

    <!-- Table header for last modified time. [CHAR_LIMIT=12] -->

    <!-- Table header for last modified time. [CHAR_LIMIT=18] -->

    <string name="sort_dimension_date">Modified</string>

    <!-- Table header for file size. [CHAR_LIMIT=12] -->

    <string name="sort_dimension_size">Size</string>