Remove outdated suppression for GpuProcessHostUIShim

tools/valgrind/memcheck/suppressions.txt

 # There are four kinds of suppressions in this file.
 # 1. third party stuff we have no control over
 #
 # 2. intentional unit test errors, or stuff that is somehow a false positive
 # in our own code, or stuff that is so trivial it's not worth fixing
 #
 # 3. Suppressions for real chromium bugs that are not yet fixed.
 # These should all be in chromium's bug tracking system (but a few aren't yet).
 # Periodically we should sweep this file and the bug tracker clean by
 # running overnight and removing outdated bugs/suppressions.
@@ skipping 2982 matching lines @@
    fun:_ZN20LayoutTestController13waitUntilDoneERKN3WTF6VectorI10CppVariantLj0EEEPS2_
    fun:_ZN13CppBoundClass14MemberCallbackI20LayoutTestControllerE3runERKN3WTF6VectorI10CppVariantLj0EEEPS5_
    fun:_ZN13CppBoundClass6invokeEPvPK10_NPVariantjPS1_
    fun:_ZN11CppNPObject6invokeEP8NPObjectPvPK10_NPVariantjPS3_
    fun:_ZN7WebCore18npObjectInvokeImplERKN2v89ArgumentsENS_18InvokeFunctionTypeE
    fun:_ZN7WebCore21npObjectMethodHandlerERKN2v89ArgumentsE
    fun:_ZN2v88internal19HandleApiCallHelperILb0EEEPNS0_11MaybeObjectENS0_47_GLOBAL__N_v8_src_builtins.cc_*BuiltinArgumentsILNS0_21BuiltinExtraArgumentsE1EEE
    obj:*
 }
 {
-   bug_73828
-   Memcheck:Leak
-   ...
-   fun:_ZN20GpuProcessHostUIShim14GetForRendererEi
-}
-{
    bug_74383a
    Memcheck:Uninitialized
    fun:gtk_widget_set_size_request
    fun:_ZN15StatusBubbleGtk22UpdateLabelSizeRequestEv
    fun:_ZN15StatusBubbleGtk19AnimationProgressedEPKN2ui9AnimationE
    fun:_ZN2ui15LinearAnimation4StepEN4base9TimeTicksE
    fun:_ZN2ui18AnimationContainer3RunEv
 }
 {
    bug_74383b
@@ skipping 2918 matching lines @@
    obj:/lib/libselinux.so.1
    obj:/lib/libselinux.so.1
 }
 {
    bug_todo_grep
    Memcheck:Leak
    fun:malloc
    obj:/bin/grep
    obj:/bin/grep
 }