Fix HTTP security header string

BMCWeb provides appropriate HTTP response headers, for example, in
header file `include/security_headers_middleware.hpp` in the
https://github.com/openbmc/bmcweb repository.

Change-Id: Ie3d85da29c6083bc3f1b7ad6ed835da1d38791d2
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/redfish/service_root/test_service_root_security.robot b/redfish/service_root/test_service_root_security.robot
index 5583a07..bf8b8f8 100644
--- a/redfish/service_root/test_service_root_security.robot
+++ b/redfish/service_root/test_service_root_security.robot
@@ -12,13 +12,13 @@
 
 ${LOGIN_SESSION_COUNT}   ${50}
 
-&{header_requirements}  strict-transport-security=max-age=31536000; includeSubdomains; preload
-...                     x-frame-options=DENY
-...                     pragma=no-cache
-...                     cache-control=no-Store,no-Cache
-...                     content-security-policy=default-src 'self'; img-src 'self' data:
-...                     x-xss-protection=1; mode=block
-...                     x-content-type-options=nosniff
+&{header_requirements}  Strict-Transport-Security=max-age=31536000; includeSubdomains; preload
+...                     X-Frame-Options=DENY
+...                     Pragma=no-cache
+...                     Cache-Control=no-Store,no-Cache
+...                     Content-Security-Policy=default-src 'self'; img-src 'self' data:
+...                     X-XSS-Protection=1; mode=block
+...                     X-Content-Type-Options=nosniff
 
 *** Test Cases ***