Silence a couple of clang-tidy warnings. (libmythtv)

There are a couple of structures that seem to have changed
significantly between Qt5 and Qt6. When clang-tidy is run against a
Qt5 based build of MythTV it recommends one action, and when run
against a Qt6 build it recommends a contrary action. (Whether to move
or copy an object when it is passed a parameter to a function.)
Silence the warning that occurs in Qt6 until that becomes the
predominant version used in releases.

mythtv/libs/libmythtv/captions/cc708window.h

@@ -111,6 +111,7 @@ class CC708CharacterAttribute
         m_underline(isUnderline),
         m_italics(isItalic),
         m_boldface(isBold),
+        // NOLINTNEXTLINE(performance-move-const-arg)
         m_actualFgColor(std::move(fgColor))
     {
     }

mythtv/libs/libmythtv/captions/subtitlescreen.h

@@ -35,6 +35,7 @@ class FormattedTextChunk
     FormattedTextChunk(QString t,
                        CC708CharacterAttribute formatting,
                        SubtitleScreen *p)
+        // NOLINTNEXTLINE(performance-move-const-arg)
         : m_text(std::move(t)), m_format(std::move(formatting)), m_parent(p) {}
     FormattedTextChunk(void) = default;