Fix test suite warning for robot 7.0 syntax

Changes:
    - Singular section headers like
      '*** Test Case ***' are deprecated.
      Use plural format like
      '*** Test Cases ***' instead.

Tested:
   - NA

Change-Id: I00a73dff4ddea75ba5bd84c2136fef1d60337ed7
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/gui/test/server_overview/test_obmc_gui_server_overview.robot b/gui/test/server_overview/test_obmc_gui_server_overview.robot
index 8ebd59c..db921f5 100644
--- a/gui/test/server_overview/test_obmc_gui_server_overview.robot
+++ b/gui/test/server_overview/test_obmc_gui_server_overview.robot
@@ -19,7 +19,7 @@
 ${xpath_launch_serial_over_lan}    //a[@class='no-icon quick-links__item']
 ${string_launch_serial_over_lan}   Serial over LAN console
 
-*** Test Case ***
+*** Test Cases ***
 # OpenBMC @ Power Off state test cases.
 
 Verify Serial Over LAN Button