android x15-v2: update boot prompt

from shell@am57xevm: to am57xevm:

Change-Id: If0c848ba895dd0f9b033515d0dda7473becdb7bc
Signed-off-by: Yongqin Liu <yongqin.liu@linaro.org>
diff --git a/android/x15-v2/template-cts-part2-v7a.yaml b/android/x15-v2/template-cts-part2-v7a.yaml
index cabb03c..a932a5c 100644
--- a/android/x15-v2/template-cts-part2-v7a.yaml
+++ b/android/x15-v2/template-cts-part2-v7a.yaml
@@ -42,7 +42,7 @@
     namespace: tlxc
     prompts:
     - 'root@(.*):/#'
-    - 'shell@am57xevm:/'
+    - 'am57xevm:/'
     timeout:
       minutes: 5
     method: lxc
@@ -93,7 +93,7 @@
     connection: serial
     prompts:
     - 'root@(.*):/#'
-    - 'shell@am57xevm:/'
+    - 'am57xevm:/'
     timeout:
       minutes: 15
     method: fastboot