Revert "Enable run-libcore-tests.sh to test specific packages"

Reason for revert: Breaks ART buildbots.

This reverts commit 9a1e6aa3db81a01e94e86aef70d09a3877987766.
diff --git a/tools/run-libcore-tests.sh b/tools/run-libcore-tests.sh
index 7dea61e..9fa580b 100755
--- a/tools/run-libcore-tests.sh
+++ b/tools/run-libcore-tests.sh
@@ -59,7 +59,7 @@
   local me=$(basename "${BASH_SOURCE[0]}")
   (
     cat << EOF
-  Usage: ${me} --mode=<mode> [options] [-- <package_to_test> ...]
+  Usage: ${me} --mode=<mode> [options]
 
   Run libcore tests using the vogar testing tool.
 
@@ -74,10 +74,6 @@
 
   The script passes unrecognized options to the command-line created for vogar.
 
-  The script runs a hardcoded list of libcore test packages by default. The user
-  may run a subset of packages by appending '--' followed by a list of package
-  names.
-
   Examples:
 
     1. Run full test suite on host:
@@ -85,9 +81,6 @@
 
     2. Run full test suite on device:
       ${me} --mode=device
-
-    3. Run tests within libcore.java.lang package on device:
-      ${me} --mode=device -- libcore.java.lang
 EOF
   ) | sed -e 's/^  //' >&2 # Strip leading whitespace from heredoc.
 }
@@ -186,12 +179,6 @@
       vogar_args="$vogar_args $1"
       gcstress=true
       ;;
-    --)
-      shift
-      # Assume remaining elements are packages to test.
-      user_packages=("$@")
-      break
-      ;;
     --help)
       usage
       exit 1
@@ -273,9 +260,7 @@
     expectations="$expectations --expectations art/tools/libcore_gcstress_debug_failures.txt"
   fi
 else
-  # We only run this package when user has not specified packages
-  # to run and not under gcstress as it can cause timeouts. See
-  # b/78228743.
+  # We only run this package when not under gcstress as it can cause timeouts. See b/78228743.
   working_packages+=("libcore.libcore.icu")
 fi
 
@@ -291,12 +276,6 @@
   vogar_args="$vogar_args --no-color"
 fi
 
-# Override working_packages if user provided specific packages to
-# test.
-if [[ ${#user_packages[@]} != 0 ]] ; then
-  working_packages=("${user_packages[@]}")
-fi
-
 # Run the tests using vogar.
 echo "Running tests for the following test packages:"
 echo ${working_packages[@]} | tr " " "\n"