tf-a-static-cppcheck: Rename variable

Not sure why but {days-to-keep} is throwing
errors on arm test CI Jenkins.

Change-Id: I1ec6520eb3c19cacb4466f48b3dc9345ec172c12
Signed-off-by: Saheer Babu <saheer.babu@arm.com>
(cherry picked from commit 540be51cf436ed28b6199207013303d0f397c365)
diff --git a/tf-a-static-cppcheck.yaml b/tf-a-static-cppcheck.yaml
index 3399910..ad55479 100644
--- a/tf-a-static-cppcheck.yaml
+++ b/tf-a-static-cppcheck.yaml
@@ -3,7 +3,7 @@
     gerrit-project: 'TF-A/trusted-firmware-a'
     gerrit-branch: 'master'
     gerrit-refspec: 'refs/heads/master'
-    days-to-keep: '180'
+    days-history: '180'
     num-to-keep: '180'
     exec-node: 'docker-amd64-tf-a-jammy'
 - scm:
@@ -38,7 +38,7 @@
     defaults: global
     properties:
         - build-discarder:
-            days-to-keep: '{days-to-keep}'
+            days-to-keep: '{days-history}'
             num-to-keep: '{num-to-keep}'
     parameters:
         - string: