Remove layout table section from H39 and H73

H39 and H73 don't need to mention layout table cases because F46 describes common failure cases of layout tables.

H39: Using caption elements to associate data table captions with data tables
http://www.w3.org/WAI/GL/2014/WD-WCAG20-TECHS-20140724/H39.html

H73: Using the summary attribute of the table element to give an overview of data tables
http://www.w3.org/WAI/GL/2014/WD-WCAG20-TECHS-20140724/H73.html

F46: Failure of Success Criterion 1.3.1 due to using th elements, caption elements, or non-empty summary attributes in layout tables
http://www.w3.org/WAI/GL/2014/WD-WCAG20-TECHS-20140724/F46.html

In this pull request, 
- Changed layout table sentence in description to a note
- Added F46 to related techniques
    - Tweaked related techniques in H39 to align with H73 and F46
- Removed layout table check procedures in tests