Suppress an invalid read in extension notifications

tools/valgrind/memcheck/suppressions.txt

Index: tools/valgrind/memcheck/suppressions.txt
diff --git a/tools/valgrind/memcheck/suppressions.txt b/tools/valgrind/memcheck/suppressions.txt
index 590c8860fb88c9720b4453d14ed7a77f6bb47c87..8e0b1b260b76fc9127c8c2b51011335aa06c1f42 100644
--- a/tools/valgrind/memcheck/suppressions.txt
+++ b/tools/valgrind/memcheck/suppressions.txt
@@ -3553,3 +3553,16 @@
    fun:sqlite3HashInsert
    fun:sqlite3EndTable
 }
+{
+   bug_47863
+   Memcheck:Addr4
+   ...
+   fun:_ZN21ExtensionsServiceTest7ObserveE16NotificationTypeRK18NotificationSourceRK19NotificationDetails
+   fun:_ZN19NotificationService6NotifyE16NotificationTypeRK18NotificationSourceRK19NotificationDetails
+   fun:_ZN17ExtensionsService21NotifyExtensionLoadedEP9Extension
+   fun:_ZN17ExtensionsService17OnExtensionLoadedEP9Extensionb
+   fun:_ZN17ExtensionsService22LoadInstalledExtensionERK13ExtensionInfob
+   fun:_ZN17ExtensionsService25ContinueLoadAllExtensionsEPSt6vectorI10linked_ptrI13ExtensionInfoESaIS3_EEN4base9TimeTicksEb
+   fun:_ZN17ExtensionsService17LoadAllExtensionsEv
+   fun:_ZN17ExtensionsService16ReloadExtensionsEv
+}