Bazel: Fix asciidoc.bzl python invocation

When invoking Documentation/replace_macros.py, bazel removes environment
using 'env -e', the python script includes '#!env python' shebang, the
result is python not found.

Alignment with js.bzl resolves the issue, explicit python removed.

Change-Id: If33baa7e7449f1a8a4a06cceefeb82dad2dc1577
Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>

tools/bzl/asciidoc.bzl

@@ -47,6 +47,7 @@ def _replace_macros_impl(ctx):
     inputs = [ctx.file._exe, ctx.file.src],
     outputs = [ctx.outputs.out],
     command = cmd,
+    use_default_shell_env = True,
     progress_message = "Replacing macros in %s" % ctx.file.src.short_path,
   )