generate_test_keys: remove left-over variable

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/tests/scripts/generate_test_keys.py b/tests/scripts/generate_test_keys.py
index 67e2abc..102593f 100755
--- a/tests/scripts/generate_test_keys.py
+++ b/tests/scripts/generate_test_keys.py
@@ -14,7 +14,6 @@
 from mbedtls_dev.asymmetric_key_data import ASYMMETRIC_KEY_DATA
 from mbedtls_dev.build_tree import guess_project_root
 
-OUTPUT_HEADER_FILE = os.path.dirname(os.path.abspath(__file__)) + "/../src/test_keys.h"
 BYTES_PER_LINE = 16
 
 def c_byte_array_literal_content(array_name: str, key_data: bytes) -> Iterator[str]: