ferrochrome-tests: Fix failure on aosp

AOSP screencap doesn't support '-a' parameter which
captures all displays.

This CL fixes the issue by not giving the parameter,
because test doesn't run with multiple displays.

Bug: 12207542
Change-Id: Icc533cf7e5497e9dccb15e0f6c2eab41cc518cca
diff --git a/tests/ferrochrome/ferrochrome.sh b/tests/ferrochrome/ferrochrome.sh
index b9b9fbc..c68e8a9 100755
--- a/tests/ferrochrome/ferrochrome.sh
+++ b/tests/ferrochrome/ferrochrome.sh
@@ -168,7 +168,7 @@
 
 adb shell mkdir -p "${fecr_screenshot_dir}"
 while [[ $((EPOCHSECONDS - fecr_start_time)) -lt ${FECR_BOOT_TIMEOUT} ]]; do
-  adb shell screencap -a -p "${fecr_screenshot_dir}/screenshot-${EPOCHSECONDS}.png"
+  adb shell screencap -p "${fecr_screenshot_dir}/screenshot-${EPOCHSECONDS}.png"
   adb shell grep -soF \""${fecr_boot_completed_log}"\" "${log_path}" && exit 0 || true
   sleep 10
 done