Update pip_parse invocation (#240)

The `requirements` argument is deprecated and will be removed in the
next rules_python release.

Fixes #239
diff --git a/fuzzing/init.bzl b/fuzzing/init.bzl
index 4e053af..f8149d8 100644
--- a/fuzzing/init.bzl
+++ b/fuzzing/init.bzl
@@ -21,6 +21,6 @@
     pip_parse(
         name = "fuzzing_py_deps",
         extra_pip_args = ["--require-hashes"],
-        requirements = "@rules_fuzzing//fuzzing:requirements.txt",
+        requirements_lock = "@rules_fuzzing//fuzzing:requirements.txt",
     )
     bazel_skylib_workspace()