Revert ThinLTO workaround (emscripten-core#26556)

Partial revert of emscripten-core#26507 
emscripten-core#26506 was fixed in LLVM.

Author: dschuff

test/codesize/test_codesize_cxx_lto.json

@@ -1,10 +1,10 @@
 {
   "a.out.js": 18563,
   "a.out.js.gz": 7666,
-  "a.out.nodebug.wasm": 101954,
-  "a.out.nodebug.wasm.gz": 39462,
-  "total": 120517,
-  "total_gz": 47128,
+  "a.out.nodebug.wasm": 101956,
+  "a.out.nodebug.wasm.gz": 39461,
+  "total": 120519,
+  "total_gz": 47127,
   "sent": [
     "a (emscripten_resize_heap)",
     "b (_setitimer_js)",

tools/system_libs.py

@@ -1091,8 +1091,6 @@ class libc(MuslInternalLibrary,
 
   def __init__(self, **kwargs):
     self.non_lto_files = self.get_libcall_files()
-    # TODO(https://github.com/emscripten-core/emscripten/issues/26506)
-    self.non_lto_files.append(utils.path_from_root('system/lib/libc/musl/src/locale/uselocale.c'))
     super().__init__(**kwargs)
 
   def get_libcall_files(self):