[doc] Fix testplan table
[doc] Fix testplan table

<br> doesn't break the line, use <li> to fix it.
And also run ./lintpy.py to fix style

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan