Our version of MPFR does not have local cache freeing abilities.

Original regression (for our cases) is: https://github.com/Qalculate/libqalculate/commit/42c5af5333c527c44b67f2d480680029c5284d49
See-also: https://github.com/Qalculate/libqalculate/pull/680
--- libqalculate-5.5.2/libqalculate/util.cc.old	2025-03-01 23:12:03.000000000 -0600
+++ libqalculate-5.5.2/libqalculate/util.cc	2025-06-28 01:32:07.292382732 -0500
@@ -1071,7 +1071,6 @@
 }
 
 void free_thread_caches() {
-	mpfr_free_cache2(MPFR_FREE_LOCAL_CACHE);
 }
 
 #ifdef _WIN32
@@ -1095,7 +1094,6 @@
 	Thread *thread = (Thread *) data;
 	SetEvent(thread->m_threadReadyEvent);
 	thread->run();
-	mpfr_free_cache2(MPFR_FREE_LOCAL_CACHE);
 	thread->running = false;
 	return 0;
 }
@@ -1145,7 +1143,6 @@
 void Thread::doCleanup(void *data) {
 	Thread *thread = (Thread *) data;
 	thread->running = false;
-	mpfr_free_cache2(MPFR_FREE_LOCAL_CACHE);
 }
 
 void Thread::enableAsynchronousCancel() {