Exclude lonely question marks from the linkify regex

Many URLs we see in the KDE rooms end with a question mark, without a
space. The linkify regex for plain URLs incorrectly considered them as
part of the link, which usually breaks them when opened in a web
browser. Now the regex excludes these, unless they are accompanied by
another character (so links like kde.org/realurl?is=true will still
work.)

(cherry picked from commit 1b7f482d0b)

src/utils.h

@@ -37,7 +37,7 @@ static const QRegularExpression strikethrough{QStringLiteral("<del>(.*?)</del>")
 static const QRegularExpression mxcImage{QStringLiteral(R"AAA(<img(.*?)src="mxc:\/\/(.*?)\/(.*?)"(.*?)>)AAA")};
 static const QRegularExpression plainUrl(
     QStringLiteral(
-        R"(<a.*?<\/a>(*SKIP)(*F)|\b((www\.(?!\.)(?!(\w|\.|-)+@)|(https?|ftp):(//)?\w|(magnet|matrix):)(&(?![lg]t;)|[^&\s<>'"])+(&(?![lg]t;)|[^&!,.\s<>'"\]):])))"),
+        R"(<a.*?<\/a>(*SKIP)(*F)|\b((www\.(?!\.)(?!(\w|\.|-)+@)|(https?|ftp):(//)?\w|(magnet|matrix):)(&(?![lg]t;)|[^&\s<>'"])+(&(?![lg]t;)|[^?&!,.\s<>'"\]):])))"),
     QRegularExpression::CaseInsensitiveOption | QRegularExpression::UseUnicodePropertiesOption);
 static const QRegularExpression
     url(QStringLiteral(R"(\b((www\.(?!\.)(?!(\w|\.|-)+@)|https?:(//)?\w)(&(?![lg]t;)|[^&\s<>'"])+(&(?![lg]t;)|[^&!,.\s<>'"\]):])))"),