Remove dedicated TextCodecUTF16

LayoutTests/fast/encoding/api/utf16-surrogates-expected.txt

Index: LayoutTests/fast/encoding/api/utf16-surrogates-expected.txt
diff --git a/LayoutTests/fast/encoding/api/utf16-surrogates-expected.txt b/LayoutTests/fast/encoding/api/utf16-surrogates-expected.txt
deleted file mode 100644
index dd90007ce06b36357f595d27db1866f6b098a710..0000000000000000000000000000000000000000
--- a/LayoutTests/fast/encoding/api/utf16-surrogates-expected.txt
+++ /dev/null
@@ -1,18 +0,0 @@
-This is a testharness.js-based test.
-FAIL utf-16le - lone surrogate lead assert_equals: expected "�" but got "���"
-FAIL utf-16le - lone surrogate lead (fatal flag set) assert_throws: function "function () {
-            new TextDecoder(t.encoding, {fa..." did not throw
-FAIL utf-16le - lone surrogate trail assert_equals: expected "�" but got "���"
-FAIL utf-16le - lone surrogate trail (fatal flag set) assert_throws: function "function () {
-            new TextDecoder(t.encoding, {fa..." did not throw
-FAIL utf-16le - unmatched surrogate lead assert_equals: expected "�\0" but got "���\0"
-FAIL utf-16le - unmatched surrogate lead (fatal flag set) assert_throws: function "function () {
-            new TextDecoder(t.encoding, {fa..." did not throw
-FAIL utf-16le - unmatched surrogate trail assert_equals: expected "�\0" but got "���\0"
-FAIL utf-16le - unmatched surrogate trail (fatal flag set) assert_throws: function "function () {
-            new TextDecoder(t.encoding, {fa..." did not throw
-FAIL utf-16le - swapped surrogate pair assert_equals: expected "��" but got "������"
-FAIL utf-16le - swapped surrogate pair (fatal flag set) assert_throws: function "function () {
-            new TextDecoder(t.encoding, {fa..." did not throw
-Harness: the test ran to completion.
-