ports-mgmt/portlint: Update to 2.21.0

• Soften the desktop-file-utils message [1]
• Avoid a bogus error on ports that append to DISTFILES. [2]
• Colorize output for warnings and errors. [3]

PR: 271623 [1]

		268681 [2]
		274981 [3]

Inspired by: yuri [3]