Accommodate change in behavior from clang-format 21 to 22

[knoepfel]

With clang-format 22, the AllowShortBlocksOnASingleLine: Always setting makes the following type of change:

diff --git a/phlex/utilities/sleep_for.hpp b/phlex/utilities/sleep_for.hpp
index 4492b8b4..9ade8c61 100644
--- a/phlex/utilities/sleep_for.hpp
+++ b/phlex/utilities/sleep_for.hpp
@@ -7,9 +7,7 @@
 namespace phlex::experimental {
   template <typename T>
   void sleep_for(T duration)
-  {
-    std::this_thread::sleep_for(duration);
-  }
+  { std::this_thread::sleep_for(duration); }

thus strictly enforcing the Always rule. This PR adjusts the setting to:

-AllowShortBlocksOnASingleLine: Always
+AllowShortBlocksOnASingleLine: Empty

thus preserving the original format. This setting should work for both clang-format 21 and 22.