build_helper_configs.py: Remove ns_target

With TF-M commit [1], users can skip specifying NS output target name in
build command line.
Remove ns_target related settings.

[1] https://review.trustedfirmware.org/c/TF-M/trusted-firmware-m/+/24353

Change-Id: I9d7602e5d6d6d2c068427c6e92e7feebd1271d18
Signed-off-by: David Hu <david.hu@arm.com>
diff --git a/build_helper/build_helper_configs.py b/build_helper/build_helper_configs.py
index cce3c66..c2e5ad0 100755
--- a/build_helper/build_helper_configs.py
+++ b/build_helper/build_helper_configs.py
@@ -74,7 +74,7 @@
 
     # CMake build commands will be executed for every build.
     "spe_cmake_build":  "cmake --build %(ci_build_root_dir)s/spe -- install",
-    "nspe_cmake_build": "cmake --build %(ci_build_root_dir)s/nspe -- %(ns_target)s",
+    "nspe_cmake_build": "cmake --build %(ci_build_root_dir)s/nspe --",
 
     "set_compiler_path": "export PATH=$PATH:$%(compiler)s_PATH",