route.8: Fix mandoc warnings

• skipping end of block that is not open: Oc
• no blank before trailing delimiter
• remove useless TN macros
• remove commented out reference for esis(4)

Differential Revision: https://reviews.freebsd.org/D38783

(cherry picked from commit 6dbfbe6e11a04f6e2ae893dbf46b059ab49eb517)