refactor(neoverse-rd): refactor scope for Neoverse RD platforms

As sgi has migrated to neoverse_rd, the scope variables would need
update. Therefore, remove the deprecated 'sgi' scope variable and
introduce the new scope variable 'neoverse-rd' to be used for any common
platform changes associated with Neoverse Reference Design platforms.

Change-Id: I5052e4573bdc7df3e6f4257146d716edd2585452
Signed-off-by: Rohit Mathew <rohit.mathew@arm.com>
diff --git a/changelog.yaml b/changelog.yaml
index b7f281c..134e72d 100644
--- a/changelog.yaml
+++ b/changelog.yaml
@@ -215,8 +215,8 @@
           - title: N1SDP
             scope: n1sdp
 
-          - title: RD
-            scope: rd
+          - title: Neoverse-RD
+            scope: neoverse-rd
 
             subsections:
               - title: RD-N1 Edge
@@ -228,13 +228,6 @@
                 deprecated:
                   - board/rdn2
 
-          - title: SGI
-            scope: sgi
-
-            deprecated:
-              - plat/sgi
-              - plat/arm/sgi
-
           - title: TC
             scope: tc