lg2: minor tweak for readability

clang-format seems to have damaged the readability of one of the
C++20 Concepts.  Add parens to improve the readability.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I0d9e591103bca0ec1d423559fffb4e2a972c3d61
diff --git a/lib/include/phosphor-logging/lg2/concepts.hpp b/lib/include/phosphor-logging/lg2/concepts.hpp
index 158df67..95d5e77 100644
--- a/lib/include/phosphor-logging/lg2/concepts.hpp
+++ b/lib/include/phosphor-logging/lg2/concepts.hpp
@@ -17,7 +17,6 @@
 
 /** Determine if a type is certainly not a constexpr string. */
 template <typename T>
-concept not_constexpr_string = !
-maybe_constexpr_string<T>;
+concept not_constexpr_string = (!maybe_constexpr_string<T>);
 
 }; // namespace lg2::details