Automerge: [Support] Remove get getThreadCount (NFC) (#150786)

getThreadCount has been deprecated for more than a year since:

  commit 744616b
  Author: Mehdi Amini <[email protected]>
  Date:   Mon Feb 19 18:07:12 2024 -0800

This patch removes it.

Author: kazutakahirata

llvm/include/llvm/Support/ThreadPool.h

@@ -149,10 +149,6 @@ class LLVM_ABI StdThreadPool : public ThreadPoolInterface {
   /// number of threads!
   unsigned getMaxConcurrency() const override { return MaxThreadCount; }
 
-  // TODO: Remove, misleading legacy name warning!
-  LLVM_DEPRECATED("Use getMaxConcurrency instead", "getMaxConcurrency")
-  unsigned getThreadCount() const { return MaxThreadCount; }
-
   /// Returns true if the current thread is a worker thread of this thread pool.
   bool isWorkerThread() const;
 
@@ -233,10 +229,6 @@ class LLVM_ABI SingleThreadExecutor : public ThreadPoolInterface {
   /// Returns always 1: there is no concurrency.
   unsigned getMaxConcurrency() const override { return 1; }
 
-  // TODO: Remove, misleading legacy name warning!
-  LLVM_DEPRECATED("Use getMaxConcurrency instead", "getMaxConcurrency")
-  unsigned getThreadCount() const { return 1; }
-
   /// Returns true if the current thread is a worker thread of this thread pool.
   bool isWorkerThread() const;