Dependencies: Update attrs, as twisted depends on newer.

requirements.txt

@@ -206,9 +206,9 @@ chardet==3.0.4 \
 idna==2.8 \
     --hash=sha256:c357b3f628cf53ae2c4c05627ecc484553142ca23264e593d327bcde5e9c3407 \
     --hash=sha256:ea8b7f6188e6fa117537c3df7da9fc686d485087abf6ac197f9c46432f7e4a3c
-attrs==21.2.0 \
-    --hash=sha256:149e90d6d8ac20db7a955ad60cf0e6881a3f20d37096140088356da6c716b0b1 \
-    --hash=sha256:ef6aaac3ca6cd92904cdd0d83f629a15f18053ec84e6432106f7a4d04ae4f5fb
+attrs==21.3.0 \
+    --hash=sha256:8f7335278dedd26b58c38e006338242cc0977f06d51579b2b8b87b9b33bff66c \
+    --hash=sha256:50f3c9b216dc9021042f71b392859a773b904ce1a029077f58f6598272432045
 requests==2.22.0 \
     --hash=sha256:11e007a8a2aa0323f5a921e9e6a2d7e4e67d9877e85773fba9ba6419025cbeb4 \
     --hash=sha256:9cf5292fcd0f598c671cfc1e0d7d1a7f13bb8085e9a590f48c010551dc6c4b31