Revert "Bump twisted from 21.2.0 to 23.8.0"

This reverts commit 9ae3c6d4a2f56d38ee7d0267975cdac593f22314.

requirements.txt

@@ -213,9 +213,9 @@ requests==2.22.0 \
     --hash=sha256:11e007a8a2aa0323f5a921e9e6a2d7e4e67d9877e85773fba9ba6419025cbeb4 \
     --hash=sha256:9cf5292fcd0f598c671cfc1e0d7d1a7f13bb8085e9a590f48c010551dc6c4b31
 # twisted
-Twisted==23.8.0 \
-    --hash=sha256:3c73360add17336a622c0d811c2a2ce29866b6e59b1125fd6509b17252098a24 \
-    --hash=sha256:b8bdba145de120ffb36c20e6e071cce984e89fba798611ed0704216fb7f884cd
+Twisted==21.2.0 \
+    --hash=sha256:77544a8945cf69b98d2946689bbe0c75de7d145cdf11f391dd487eae8fc95a12 \
+    --hash=sha256:aab38085ea6cda5b378b519a0ec99986874921ee8881318626b0a3414bb2631e
 constantly==15.1.0 \
     --hash=sha256:586372eb92059873e29eba4f9dec8381541b4d3834660707faf8ba59146dfc35 \
     --hash=sha256:dd2fa9d6b1a51a83f0d7dd76293d734046aa176e384bf6e33b7e44880eb37c5d