runner/templates/testrun.html: Wrap failure reason to multiple lines
runner/templates/testrun.html: Wrap failure reason to multiple lines

`white-space: pre` CSS property prevents the browser from wrapping the
text to multiple lines if it is too long; as a result, in many cases part
of the failure reason gets out of screen, even when the browser is expanded
to full screen.

stb-tester/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,wmanley/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,wmanley/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,wmanley/stb-tester,wmanley/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,wmanley/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester,martynjarvis/stb-tester