GH-103805: Lib test f541 linting issue fix (#103812)

This PR makes some minor linting adjustments to the Lib/test module
caught by [ruff](https://github.com/charliermarsh/ruff). The adjustments
are all related to the `F541 f-string without any placeholders` issue.

Issue: https://github.com/python/cpython/issues/103805

<!-- gh-issue-number: gh-103805 -->
* Issue: gh-103805
<!-- /gh-issue-number -->

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Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
Co-authored-by: Gregory P. Smith <greg@krypto.org>

Lib/test/test_embed.py

@@ -110,7 +110,7 @@ class EmbeddingTestsMixin:
             print(f"--- {cmd} failed ---")
             print(f"stdout:\n{out}")
             print(f"stderr:\n{err}")
-            print(f"------")
+            print("------")
 
         self.assertEqual(p.returncode, returncode,
                          "bad returncode %d, stderr is %r" %