Fix various spelling errors still found in code (#7785)

Summary:
dont -> don't
refered -> referred

Merging this would allow to decrease the size of the downstream patch at https://salsa.debian.org/mariadb-team/mariadb-10.5/-/blob/master/debian/patches/fix-spelling.patch

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7785

Reviewed By: akankshamahajan15

Differential Revision: D25761408

Pulled By: jay-zhuang

fbshipit-source-id: 290406ef2a3b05a3daeedbe3b20a00798ef581e7

include/rocksdb/cache.h

@@ -59,10 +59,10 @@ struct LRUCacheOptions {
 
   // Percentage of cache reserved for high priority entries.
   // If greater than zero, the LRU list will be split into a high-pri
-  // list and a low-pri list. High-pri entries will be insert to the
+  // list and a low-pri list. High-pri entries will be inserted to the
   // tail of high-pri list, while low-pri entries will be first inserted to
-  // the low-pri list (the midpoint). This is refered to as
+  // the low-pri list (the midpoint). This is referred to as
-  // midpoint insertion strategy to make entries never get hit in cache
+  // midpoint insertion strategy to make entries that never get hit in cache
   // age out faster.
   //
   // See also