Bump requests from 2.20.1 to 2.21.0 (#1555)

Bumps [requests](https://github.com/requests/requests) from 2.20.1 to 2.21.0.
- [Release notes](https://github.com/requests/requests/releases)
- [Changelog](https://github.com/requests/requests/blob/master/HISTORY.md)
- [Commits](https://github.com/requests/requests/compare/v2.20.1...v2.21.0)

Signed-off-by: dependabot[bot] <support@dependabot.com>

requirements/build.txt

@@ -28,9 +28,9 @@ newrelic==4.10.0.112 \
 django-session-csrf==0.7.1 \
     --hash=sha256:e17177e6e2e6518ec7ce6693ad10a5c747f8571d09f4cfa9082599334421605d \
     --hash=sha256:ff8c10e30d312c77fc6a6db7710e22b9383e28c03b7fe958876ca96f39aa6cf2
-requests==2.20.1 \
-    --hash=sha256:65b3a120e4329e33c9889db89c80976c5272f56ea92d3e74da8a463992e3ff54 \
-    --hash=sha256:ea881206e59f41dbd0bd445437d792e43906703fff75ca8ff43ccdb11f33f263
+requests==2.21.0 \
+    --hash=sha256:7bf2a778576d825600030a110f3c0e3e8edc51dfaafe1c146e39a2027784957b \
+    --hash=sha256:502a824f31acdacb3a35b6690b5fbf0bc41d63a24a45c4004352b0242707598e
 boto3==1.7.77 \
     --hash=sha256:7fdc2f6f21372572fec9df52e70b5ae11c263fe5905fc61dbd7ac3b01350cb4a \
     --hash=sha256:e3ac48844b5ee6adafd27f6682efdd009a9c5f70abef0b72092d039ae3050279