Update clang-format in Travis

AllowShortBlocksOnASingleLine: Empty was added in clang-format 10

.travis.yml

@@ -31,7 +31,7 @@ _apt_pkgs: &_apt_pkgs
   - 'gdb'
   - 'lcov'
   - 'cppcheck'
-  - 'clang-format-9'
+  - 'clang-format-10'
   - 'python3-pip'
   - 'python3-setuptools'
   - 'ninja-build'
@@ -227,7 +227,7 @@ jobs:
 before_install:
   # Check source code formatting
   - if [ $TRAVIS_PULL_REQUEST != "false" ]; then changed_src=$(git diff --name-only master...HEAD | egrep "\.(h|cc)$" | grep -v "include/pistache/thirdparty" || [ $? == 1 ]); fi
-  - if [ ! -z "$changed_src" ]; then git-clang-format-9 --quiet --binary $(which clang-format-9) --diff master HEAD -- $changed_src > ./clang-format-diff; fi
+  - if [ ! -z "$changed_src" ]; then git-clang-format-10 --quiet --binary $(which clang-format-10) --diff master HEAD -- $changed_src > ./clang-format-diff; fi
   - if [ -s ./clang-format-diff ]; then cat ./clang-format-diff && echo "Format source code according to .clang-format rules. Make sure to run make format" && false; fi
 
 install: