[Conan] fix building Boost.Locale with Apple-clang in versions >= 1.81

CI/conan/base/apple

@@ -3,6 +3,10 @@ compiler=apple-clang
 compiler.version=13
 compiler.libcxx=libc++
 build_type=Release
+
+# required for Boost.Locale in versions >= 1.81
+compiler.cppstd=11
+
 [conf]
 tools.apple:enable_bitcode = False
 tools.cmake.cmaketoolchain:generator = Ninja