x11/kitty: Use BUILD_DEPENDS= x11-fonts/nerd-fonts-symbols

• The build dependency x11-fonts/nerd-fonts was split into subports in commit 5ab056a5f85f709d8a6d7eb6582a94c85df37de5. Kitty requires only the Symbols font, so the port can switch to the more lightweight subport.
• Don't bump PORTREVISION because the resulting package does not change.

PR: 293280