Remove F48

Remove F48,

- it's same as F34
- considering CSS white-space property,  it can be said that any HTML elements may have white-space formatted information 

F34: Failure of Success Criterion 1.3.1 and 1.3.2 due to using white space characters to format tables in plain text content
http://www.w3.org/WAI/GL/2014/WD-WCAG20-TECHS-20140724/F34.html

F48: Failure of Success Criterion 1.3.1 due to using the pre element to markup tabular information
http://www.w3.org/WAI/GL/2014/WD-WCAG20-TECHS-20140724/F48.html