net/messagelib: remove unnecessary dependency on webkit

Was dropped upstream in [1].

[1] https://invent.kde.org/pim/messagelib/-/commit/9401e0ea60ac3346ac22bcca8e4639d5b2287ebf

net/messagelib/Makefile

@@ -1,5 +1,6 @@
 PORTNAME=	messagelib
 DISTVERSION=	${KDE_APPLICATIONS_VERSION}
+PORTREVISION=	1
 CATEGORIES=	net kde kde-applications
 
 MAINTAINER=	kde@FreeBSD.org
@@ -20,7 +21,7 @@ USES=		cmake compiler:c++11-lib cpe gettext grantlee:5 kde:5 qca \
 CPE_VENDOR=	kde
 USE_KDE=	archive auth bookmarks codecs completion config configwidgets \
 		coreaddons guiaddons i18n iconthemes imap itemmodels itemviews jobwidgets \
-		kdewebkit kio notifications service solid sonnet syntaxhighlighting \
+		kio notifications service solid sonnet syntaxhighlighting \
 		textwidgets wallet widgetsaddons windowsystem xmlgui \
 		ecm:build
 # pim components