Increase the number of items for ooc merge sorts

Author: FrancescAlted

src/blosc2/indexing.py

@@ -75,7 +75,7 @@
 _GATHER_MMAP_HANDLES: dict[str, object] = {}
 _HOT_CACHE_GLOBAL_SCOPE = ("global", 0)
 
-FULL_OOC_RUN_ITEMS = 2_000_000
+FULL_OOC_RUN_ITEMS = 8_000_000
 FULL_OOC_MERGE_BUFFER_ITEMS = 500_000
 FULL_SELECTIVE_OOC_MAX_SPANS = 128
 FULL_RUN_BOUNDED_FALLBACK_RUNS = 8