Use DEFAULT_MAX_PERMITS constant in getSharedArenaMaxPermitsSysprop (#15908)

* adjust SharedArenaMaxPermits to RefCountedSharedArena.DEFAULT_MAX_PERMITS

* add changes

* move change entry to 10.5

Author: Huaixinww

lucene/CHANGES.txt

@@ -325,6 +325,10 @@ Bug Fixes
 * GITHUB#15878: Fix existential quantification bug in caller checks
   (VectorizationProvider, TestSecrets).  (Uwe Schindler)
 
+* GITHUB#15908: Fix MMapDirectory.getSharedArenaMaxPermitsSysprop() to use
+  RefCountedSharedArena.DEFAULT_MAX_PERMITS instead of a hardcoded value, so that
+  the default change from GITHUB#15078 takes effect. (Huaixinww)
+
 Other
 ---------------------
 * GITHUB#15586: Document that scoring and ranking may change across major Lucene versions, and that applications requiring stable ranking should explicitly configure Similarity. (Parveen Saini)

lucene/core/src/java/org/apache/lucene/store/MMapDirectory.java

@@ -482,7 +482,7 @@ private static int checkMaxPermits(int maxPermits) {
   }
 
   private static int getSharedArenaMaxPermitsSysprop() {
-    int ret = 1024; // default value
+    int ret = RefCountedSharedArena.DEFAULT_MAX_PERMITS;
     try {
       String str = System.getProperty(SHARED_ARENA_MAX_PERMITS_SYSPROP);
       if (str != null) {