cleanup directory class and in favor of <filename> in arch-handbook

[jgh]

Summary

cleanup directory class and in favor of <filename> in arch-handbook

[wblock]

The class="directory" attribute was removed, but the paragraph was re-wrapped, so there are lines on which only whitespace changes have been made.

Just remove the tags, leaving short lines. Then you or some other person (sometimes me) can do one big whitespace sweep to the whole file at some future point.

[jgh]

just removed tags

[wblock]

Perfect! Please build-test before commit.