IVGCVSW-5293 Remove boost::format from armnn/tests

 * Replaced boost::format with fmt::format

Signed-off-by: James Ward <james.ward@arm.com>
Change-Id: Icf5a6508e7be3d31bc063643491fc5e0607f21fa
diff --git a/tests/InferenceTest.inl b/tests/InferenceTest.inl
index 362be7b..4a97d17 100644
--- a/tests/InferenceTest.inl
+++ b/tests/InferenceTest.inl
@@ -6,8 +6,8 @@
 
 #include <armnn/utility/Assert.hpp>
 #include <boost/numeric/conversion/cast.hpp>
-#include <boost/format.hpp>
 #include <boost/program_options.hpp>
+#include <fmt/format.h>
 
 #include <fstream>
 #include <iostream>
@@ -288,8 +288,8 @@
         }
         else
         {
-            throw armnn::Exception(boost::str(boost::format("Failed to open input validation file: %1%")
-                % m_ValidationFileIn));
+            throw armnn::Exception(fmt::format("Failed to open input validation file: {}"
+                , m_ValidationFileIn));
         }
     }
 }