www/lexbor: Update 2.5.0 => 2.6.0

Changelogs:

• https://github.com/lexbor/lexbor/releases/tag/v2.6.0
• https://github.com/lexbor/lexbor/compare/v2.5.0...v2.6.0

• Use PORTEXAMPLES=* to simplify pkg-plist
• Pet portclippy(1) and portfmt(1)

Approved by: db@, yuri@ (Mentors, implicit)
Differential Revision: https://reviews.freebsd.org/D53990