CMake: Disable doc_snippets feature for static builds

Now that we have a separate feature, we can fix QTBUG-99063 by disabling
the doc_snippets feature globally.

Task-number: QTBUG-99063
Change-Id: I77ba875633ed89fdd8b8481ea0fddc7e91cbb9ca
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>

configure.cmake

@@ -587,6 +587,7 @@ qt_feature("private_tests" PRIVATE
 qt_feature("doc_snippets" PRIVATE
     LABEL "Developer build: doc_snippets"
     AUTODETECT QT_FEATURE_developer_build
+    CONDITION QT_FEATURE_shared
 )
 qt_feature_definition("developer-build" "QT_BUILD_INTERNAL")
 qt_feature_config("developer-build" QMAKE_PUBLIC_QT_CONFIG