Remove suppressions for two reliability_tests errors that were fixed

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 # running overnight and removing outdated bugs/suppressions.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 1127 matching lines @@
    fun:_ZN2pp25CompletionCallbackFactoryI15TestingInstanceNS_22ThreadSafeThreadTraitsEE11Dispatcher0IMS1_FviEEclEPS1_i
    fun:_ZN2pp25CompletionCallbackFactoryI15TestingInstanceNS_22ThreadSafeThreadTraitsEE12CallbackDataINS3_11Dispatcher0IMS1_FviEEEE5ThunkEPvi
 }
 {
   intentional_see_bug_156466
   Memcheck:Leak
   fun:_Znw*
   fun:_ZN3ash5ShellC1EPNS_13ShellDelegateE
   fun:_ZN3ash5Shell14CreateInstanceEPNS_13ShellDelegateE
 }
-{
-   bug_163902
-   Memcheck:Param
-   socketcall.sendto(msg)
-   ...
-   fun:_ZN3net8internal19AddressTrackerLinux4InitEv
-   fun:_ZN3net26NetworkChangeNotifierLinux6Thread4InitEv
-}
-{
-   bug_163904
-   Memcheck:Param
-   exit_group(status)
-   fun:SyscallAsm
-   fun:_ZN11playground214SandboxSyscallEiz
-   fun:_ZN11playground23Die9ExitGroupEv
-   fun:_ZN11playground23Die10SandboxDieEPKcS2_i
-   fun:_ZN11playground27Sandbox13installFilterEb
-}
 
 #-----------------------------------------------------------------------
 # 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).
 
 {
    # Chromium flakily leaks tasks at shutdown, see
    # http://crbug.com/6532
    # http://codereview.chromium.org/20067
    # http://codereview.chromium.org/42083
@@ skipping 5108 matching lines @@
 }
 {
    bug_163924
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN24JSONAsynchronousUnpacker6CreateEP32JSONAsynchronousUnpackerDelegate
    fun:_ZN18WebResourceService18OnURLFetchCompleteEPKN3net10URLFetcherE
    fun:_ZN3net14URLFetcherCore29InformDelegateFetchIsCompleteEv
    fun:_ZN3net14URLFetcherCore21OnCompletedURLRequestEN4base9TimeDeltaE
 }