Summary
-------

Obsolete the no longer used flag UseCounterDecay and also schedule its expiration.


Problem
-------

The flag UseCounterDecay has no effect as of JDK-8251462.

Solution
--------

Obsolete UseCounterDecay in JDK 22 and expire it in JDK 23.

Specification
-------------

The relevant changes for this CSR:
```
diff --git a/src/hotspot/share/runtime/arguments.cpp b/src/hotspot/share/runtime/arguments.cpp
index c790a0022a4..a503e72d692 100644
--- a/src/hotspot/share/runtime/arguments.cpp
+++ b/src/hotspot/share/runtime/arguments.cpp
@@ -529,6 +529,7 @@ static SpecialFlag const special_jvm_flags[] = {
   { "RefDiscoveryPolicy",           JDK_Version::undefined(), JDK_Version::jdk(21), JDK_Version::undefined() },
   { "MetaspaceReclaimPolicy",       JDK_Version::undefined(), JDK_Version::jdk(21), JDK_Version::undefined() },
   { "DoReserveCopyInSuperWord",     JDK_Version::undefined(), JDK_Version::jdk(22), JDK_Version::jdk(23) },
+  { "UseCounterDecay",              JDK_Version::undefined(), JDK_Version::jdk(22), JDK_Version::jdk(23) },
 
 #ifdef LINUX
   { "UseHugeTLBFS",                 JDK_Version::undefined(), JDK_Version::jdk(22), JDK_Version::jdk(23) },
diff --git a/src/hotspot/share/runtime/globals.hpp b/src/hotspot/share/runtime/globals.hpp
index 17dfaee8a76..b780b040f94 100644
--- a/src/hotspot/share/runtime/globals.hpp
+++ b/src/hotspot/share/runtime/globals.hpp
@@ -1220,16 +1220,9 @@ const int ObjectAlignmentInBytes = 8;
   product(bool, UseCompiler, true,                                          \
           "Use Just-In-Time compilation")                                   \
                                                                             \
-  product(bool, UseCounterDecay, true,                                      \
-          "Adjust recompilation counters")                                  \
-                                                                            \
   develop(intx, CounterHalfLifeTime,    30,                                 \
           "Half-life time of invocation counters (in seconds)")             \
                                                                             \
```

Full PR for reference: https://github.com/openjdk/jdk/pull/16673