ci: remove duplicated KBS test case

KBS Build with default feature and KBS build with built-in CoCo AS
feature are the same, thus we delete the duplicated one and add more
information.

Signed-off-by: Xynnn007 <xynnn@linux.alibaba.com>

.github/workflows/kbs-rust.yml

@@ -52,11 +52,7 @@ jobs:
         sudo apt-get update
         sudo apt-get install -y libtdx-attest-dev libsgx-dcap-quote-verify-dev
 
-    - name: KBS Build [Default]
-      working-directory: kbs
-      run: make
-
-    - name: KBS Build [Built-in CoCo AS]
+    - name: KBS Build [Default/Built-in CoCo AS]
       working-directory: kbs
       run: make