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/security/test_slp.robot b/security/test_slp.robot
index fb95aa1..f0892f3 100644
--- a/security/test_slp.robot
+++ b/security/test_slp.robot
@@ -55,7 +55,7 @@
     ${rc}  ${output}=  Run And Return Rc And Output
     ...   slptool -u ${OPENBMC_HOST} ${cmd} ${param}
     Should Be Equal As Integers  ${rc}  0
-    [Return]  ${output}
+    RETURN  ${output}
 
 Verify Service Types
     [Documentation]  Verifies the output of service types.