Fix setup.py to read dependencies from requirements.in instead of requirements.txt

The previous implementation incorrectly parsed pip-compile generated
requirements.txt which included comment lines. This fix properly reads
from the source requirements.in file and filters out comments and empty
lines, ensuring only pycasbin (not casbin) is used as a dependency.

Co-authored-by: hsluoyz <3787410+hsluoyz@users.noreply.github.com>

Author: Copilot

setup.py

@@ -13,10 +13,10 @@
 print(long_description)
 
 # get the dependencies and installs
-with open(path.join(here, "requirements.txt"), encoding="utf-8") as f:
+with open(path.join(here, "requirements.in"), encoding="utf-8") as f:
     all_reqs = f.read().split("\n")
 
-install_requires = [x.strip() for x in all_reqs if "git+" not in x]
+install_requires = [x.strip() for x in all_reqs if x.strip() and not x.startswith("#") and "git+" not in x]
 dependency_links = [
     x.strip().replace("git+", "") for x in all_reqs if x.startswith("git+")
 ]