Drop some unused Memcheck:Unaddressable suppressions, widen one TSan one.

tools/valgrind/tsan/suppressions.txt

 # There are a few 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 # running overnight and removing outdated bugs/suppressions.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 113 matching lines @@
 }
 
 ############################
 # 1.3 Benign races in SQLLite
 # TODO(timurrr|oshima): following four suppressions could be obsolete.
 {
   Two writes, same value (SQLLite pthreadMutexAlloc)
   ThreadSanitizer:Race
   ...
   fun:pthreadMutexAlloc
-  fun:sqlite3MutexAlloc
-}
-
-{
-  Two writes, same value 2 (SQLLite pthreadMutexAlloc)
-  ThreadSanitizer:Race
-  fun:pthreadMutexAlloc
-  ...
-  fun:openDatabase
 }
 
 {
   Two writes, same value (under sqlite3Malloc)
   ThreadSanitizer:Race
   ...
   fun:sqlite3Malloc*
 }
 
 {
@@ skipping 727 matching lines @@
 }
 {
   bug_118345
   ThreadSanitizer:Race
   fun:base::Thread::message_loop
   fun:content::BrowserThreadImpl::PostTaskHelper
   fun:content::BrowserThread::PostTask
   fun:PluginLoaderPosix::GetPluginsToLoad
   fun:base::internal::RunnableAdapter::Run
 }