Remove heapcheck suppression for media_unittests.

tools/heapcheck/suppressions.txt

 # There are three 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 # running overnight and removing outdated bugs/suppressions.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 1226 matching lines @@
 }
 {
    bug_71909
    Heapcheck:Leak
    fun:TestingProfile::CreateRequestContext
    fun:MockService
    ...
    fun:ExtensionUpdaterTest*
 }
 {
-   bug_73132
-   Heapcheck:Leak
-   fun:Callback1::Type* NewCallback
-   fun:media::PipelineImpl::Initialize*
-   fun:media::PipelineImpl::InitializeTask
-}
-{
    bug_73268a
    Heapcheck:Leak
    ...
    fun:ExtensionSpecialStoragePolicy::SpecialCollection::Contains
    fun:ExtensionSpecialStoragePolicy::IsStorage*
    fun:ExtensionSpecialStoragePolicyTest_*_Test::TestBody
 }
 {
    bug_73268b
    Heapcheck:Leak
    ...
    fun:bool ::InitCanonical
    fun:GURL
    ...
    fun:ExtensionSpecialStoragePolicyTest_*
 }