Merge bitcoin#17086: tests: Fix fs_tests for unknown locales

d48f664 tests: Fix fs_tests for unknown locales (Daki Carnhof)

Pull request description:

  Fix by removing "L" as suggested by meeDamian in
  bitcoin#14948 (comment)

  ```
  # all in .../bitcoin/src/test
  $ uname -m
  x86_64
  $ export LC_ALL=randomnonexistentlocale
  $ ./test_bitcoin
  Running 369 test cases...
  unknown location(0): fatal error: in "fs_tests/fsbridge_fstream": boost::system::system_error: boost::filesystem::path codecvt to string: error
  test/fs_tests.cpp(13): last checkpoint: "fsbridge_fstream" test entry

  *** 1 failure is detected in the test module "Bitcoin Core Test Suite"
  ```

  After the patch is applied, the same test under the same conditions runs fine.

  ```
  $ export LC_ALL=randomnonexistentlocale
  $ ./test_bitcoin
  Running 369 test cases...

  *** No errors detected
  ```

  Co-Authored-By: bugs@meedamian.com

ACKs for top commit:
  laanwj:
    ACK d48f664

Tree-SHA512: a9910252b8ce6a05cab5530874549c2999ca2c28e835fc18aa8e5468fb417bd7d245864ec71d9233dd53e02940a9f0691b247430257f27eb0d7c20745d1c846d

src/test/fs_tests.cpp

@@ -14,7 +14,7 @@ BOOST_AUTO_TEST_CASE(fsbridge_fstream)
     fs::path tmpfolder = SetDataDir("fsbridge_fstream");
     // tmpfile1 should be the same as tmpfile2
     fs::path tmpfile1 = tmpfolder / "fs_tests_₿_🏃";
-    fs::path tmpfile2 = tmpfolder / L"fs_tests_₿_🏃";
+    fs::path tmpfile2 = tmpfolder / "fs_tests_₿_🏃";
     {
         fsbridge::ofstream file(tmpfile1);
         file << "bitcoin";