Remove references to cffi

We no longer use `cffi` since we don't build any C code anymore.

Author: jlaine

MANIFEST.in

@@ -5,6 +5,5 @@ recursive-include docs *.py *.rst *.svg Makefile
 recursive-include examples *.html *.js *.py *.rst *.wav
 recursive-include requirements *.txt
 recursive-include scripts *.json *.py
-recursive-include src/_cffi_src *.py
 recursive-include stubs *.pyi
 recursive-include tests *.bin *.py

pyproject.toml

@@ -27,7 +27,6 @@ classifiers = [
 dependencies = [
     "aioice>=0.10.1,<1.0.0",
     "av>=14.0.0,<15.0.0",
-    "cffi>=1.0.0",
     "cryptography>=44.0.0",
     "google-crc32c>=1.1",
     "pyee>=13.0.0",
@@ -79,5 +78,4 @@ known-third-party = ["aiortc"]
 version = {attr = "aiortc.__version__"}
 
 [tool.setuptools.packages.find]
-exclude = ["_cffi_src"]
 where = ["src"]