Bump downstream dependencies in CI (#15705)

Author: pyca-boringbot[bot]

.github/workflows/ci.yml

@@ -410,13 +410,13 @@ jobs:
             PATH: josepy
           - DOWNSTREAM: mitmproxy
             REPO: mitmproxy/mitmproxy
-            # Latest commit on the mitmproxy main branch, as of Sep 10, 2026.
-            REF: b506c68108e287104045333ade476d92c39c275e
+            # Latest commit on the mitmproxy main branch, as of Sep 27, 2026.
+            REF: d0d5a70be9bfc4f99e6d90e4aa10acc142b85d21
             PATH: mitmproxy
           - DOWNSTREAM: scapy
             REPO: secdev/scapy
-            # Latest commit on the scapy master branch, as of Sep 24, 2026.
-            REF: e4742a53e5d1d66d76406560e4977d7a1d9fd8b3
+            # Latest commit on the scapy master branch, as of Sep 27, 2026.
+            REF: c5e9a5b0cd25f4d0bb87c3b208db342edea7da38
             PATH: scapy
           - DOWNSTREAM: sigstore-python
             REPO: sigstore/sigstore-python