Merge bitcoin#18879: valgrind: remove outdated suppressions

d7120f7 valgrind : remove duplicate BCLog::Logger suppression (fanquake)
708e3c7 valgrind: remove rest_blockhash_by_height suppression (fanquake)

Pull request description:

  bitcoin@708e3c7: `Suppress rest_blockhash_by_height` should no longer be needed after bitcoin#18785.

  bitcoin@d7120f7 : Removes a duplicate `Suppress BCLog::Logger::StartLogging()` suppression that was added in bitcoin#17770.

ACKs for top commit:
  MarcoFalke:
    ACK d7120f7
  practicalswift:
    ACK d7120f7 -- patch looks correct and valgrind Travis job is happy

Tree-SHA512: 45f5b9fa64bf83cada3cd9ad33c245f660376d5b29f51a2531d83133940090df945f5ef26c5847d6ec024ffab9528d55573c5cf9ca5e73795f9abfc971b3d29b

contrib/valgrind.supp

@@ -184,16 +184,3 @@
    ...
    fun:_ZN5BCLog6Logger12StartLoggingEv
 }
-{
-   Suppress BCLog::Logger::StartLogging() still reachable memory warning
-   Memcheck:Leak
-   match-leak-kinds: reachable
-   fun:malloc
-   ...
-   fun:_ZN5BCLog6Logger12StartLoggingEv
-}
-{
-   Suppress rest_blockhash_by_height Conditional jump or move depends on uninitialised value(s)
-   Memcheck:Cond
-   fun:_ZL24rest_blockhash_by_heightP11HTTPRequestRKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE
-}