Enable shared_dictionary for quality 3 and 4.

PiperOrigin-RevId: 781972185

c/enc/backward_references.c

diff --git a/c/enc/backward_references.c b/c/enc/backward_references.c
index 805c001..94fd704 100644
--- a/c/enc/backward_references.c
+++ b/c/enc/backward_references.c
@@ -133,14 +133,6 @@
 #define PREFIX() D
 #define ENABLE_COMPOUND_DICTIONARY 1
 
-#define HASHER() H3
-/* NOLINTNEXTLINE(build/include) */
-#include "backward_references_inc.h"
-#undef HASHER
-#define HASHER() H4
-/* NOLINTNEXTLINE(build/include) */
-#include "backward_references_inc.h"
-#undef HASHER
 #define HASHER() H5
 /* NOLINTNEXTLINE(build/include) */
 #include "backward_references_inc.h"
@@ -202,8 +194,6 @@
             literal_context_lut, params, hasher, dist_cache,        \
             last_insert_len, commands, num_commands, num_literals); \
         return;
-      CASE_(3)
-      CASE_(4)
       CASE_(5)
       CASE_(6)
 #if defined(BROTLI_MAX_SIMD_QUALITY)