DEPS: Update leveldatabase from 1.18 to 1.20.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 1c9bb954acc172fdc2c56d5fd2b2375273cbb6ae..d783ebe8c048dbe6f25ff7afea1cbfedbdc80618 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -774,22 +774,7 @@ group("gn_only") {
       "//third_party/angle:libANGLE",
       "//third_party/angle:libEGL",
       "//third_party/angle:libGLESv2",
-      "//third_party/leveldatabase:leveldb_arena_test",
-      "//third_party/leveldatabase:leveldb_bloom_test",
-      "//third_party/leveldatabase:leveldb_cache_test",
-      "//third_party/leveldatabase:leveldb_corruption_test",
-      "//third_party/leveldatabase:leveldb_crc32c_test",
-      "//third_party/leveldatabase:leveldb_db_bench",
-      "//third_party/leveldatabase:leveldb_db_test",
-      "//third_party/leveldatabase:leveldb_dbformat_test",
-      "//third_party/leveldatabase:leveldb_env_test",
-      "//third_party/leveldatabase:leveldb_filename_test",
-      "//third_party/leveldatabase:leveldb_filter_block_test",
-      "//third_party/leveldatabase:leveldb_log_test",
-      "//third_party/leveldatabase:leveldb_skiplist_test",
-      "//third_party/leveldatabase:leveldb_table_test",
-      "//third_party/leveldatabase:leveldb_version_edit_test",
-      "//third_party/leveldatabase:leveldb_write_batch_test",
+      "//third_party/leveldatabase:leveldb_test_targets",
       "//third_party/libjpeg_turbo:simd",
       "//third_party/opus:opus_compare",
       "//third_party/opus:opus_demo",