Robot Framework 7.0 changes

Update robot code syntax overall in the repo

Changes:
   - Update the requirement.txt package version for robot
   - The '[Return]' setting is deprecated.
      Use the 'RETURN' statement instead.
   - Singular section headers like '*** Test Case ***'
     are deprecated. Use plural format like
     '*** Test Cases ***' instead.
   - Singular section headers like '*** Variable ***'
     are deprecated

Tested:
   - Ran from sandbox with the version
     $ robot --version
     Robot Framework 7.0 (Python 3.10.12 on linux)

     and also tested on latest python version

     Robot Framework 7.0 (Python 3.11.9 on linux)

Change-Id: I54e85f9d799556c63b9a39f79483f83e9b980768
Signed-off-by: George Keishing <gkeishin@in.ibm.com>
diff --git a/gui/lib/resource.robot b/gui/lib/resource.robot
index ee29a61..038d135 100644
--- a/gui/lib/resource.robot
+++ b/gui/lib/resource.robot
@@ -65,7 +65,7 @@
     ...     Set Variable  windows
     ...   ELSE
     ...     Run  uname
-    [Return]  ${op_system}
+    RETURN  ${op_system}
 
 Launch Header Browser
     [Documentation]  Open the browser with the URL and
@@ -93,7 +93,7 @@
     ${browser_ID}=  Open Browser  ${URL}
     Set Window Size  1920  1080
 
-    [Return]  ${browser_ID}
+    RETURN  ${browser_ID}
 
 Login OpenBMC GUI
     [Documentation]  Perform login to open BMC GUI.
@@ -228,7 +228,7 @@
     ...  Launch Headless Browser  ${URL}  ${browser}
     ...  ELSE  Open Browser  ${URL}  ${browser}
 
-    [Return]  ${browser_ID}
+    RETURN  ${browser_ID}
 
 
 Controller Server Power Click Button