Remove IWYU pragmas

These were added as part of
d5c80ad9c07b94465d8ea62d2b6f87c30cac765e: test treewide: iwyu

Since then, Nan hasn't been very active on the project, and to my
knowledge, since the initial run, we've never used IWYU again.

clang-include-cleaner seems to work well without needing these pragmas,
and is what we're using, even if it's less useful than IWYU.

Remove all mention of IWYU.

Tested: Code compiles.

Change-Id: I06feedeeac9a114f5bdec81d59ca83223efd8aa7
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/test/http/mutual_tls.cpp b/test/http/mutual_tls.cpp
index e354466..bb3cbbf 100644
--- a/test/http/mutual_tls.cpp
+++ b/test/http/mutual_tls.cpp
@@ -21,7 +21,7 @@
 #include <memory>
 
 #include <gmock/gmock.h>
-#include <gtest/gtest.h> // IWYU pragma: keep
+#include <gtest/gtest.h>
 
 using ::testing::IsNull;
 using ::testing::NotNull;