qt/qtbase: enable printsupport (was -DFEATURE_printsupport=OFF)

Qt6PrintSupport ships inside qtbase (src/printsupport) — it was disabled, not
missing. konsole and 8 KDE packages (kxmlgui, kwin, plasma-desktop, ...) need
Qt6::PrintSupport; enable it rather than working around its absence.

local/recipes/qt/qtbase/recipe.toml

@@ -688,7 +688,7 @@ cmake "${COOKBOOK_SOURCE}" \
      -DFEATURE_process=ON \
      -DFEATURE_testlib=OFF \
     -DFEATURE_sql=OFF \
-    -DFEATURE_printsupport=OFF \
+    -DFEATURE_printsupport=ON \
     -DFEATURE_system_zlib=ON \
     -DFEATURE_system_pcre2=OFF \
     -DFEATURE_system_doubleconversion=OFF \