Update clang-format version used by CircleCI (#261)

Summary:
Pull Request resolved: #261

Facebook's internal version of clang-format got updated to v11 over the weekend and this apparently changed the formatting. I think this was a "bugfix", because the `AlignAfterOpenBracket`, which we've set to `AlwaysBreak`, was supposed to also cover curly brackets, but it seems it didn't, whereas now it does. I "bisected" this and it appears the change was introduces in clang-format v10. This is good because v11 isn't available on Ubuntu 18.04, which is what we use in CircleCI, whereas v10 is.

Reviewed By: patricklabatut

Differential Revision: D25867695

fbshipit-source-id: ae98b9e9befee3c86a28820988b9fc3735557e52

.circleci/config.yml

@@ -244,11 +244,11 @@ jobs:
           name: Install clang-format
           command: |
             apt-get update
-            apt-get install -y git-core clang-format-8
+            apt-get install -y git-core clang-format-10
       - run:
           name: Verify clang-format
           command: |
-             git ls-files | grep -E  '.[cc|h]$' | xargs clang-format-8 -i
+             git ls-files | grep -E  '.[cc|h]$' | xargs clang-format-10 -i
              if git diff --quiet; then
                echo "Formatting OK!"
              else