Use C++11 brace style in clang-format

Signed-off-by: Felix Weilbach <felix.weilbach@nextcloud.com>

.clang-format

@@ -61,3 +61,5 @@ ForEachMacros:   [ foreach, Q_FOREACH, BOOST_FOREACH, forever, Q_FOREVER, QBENCH
 MaxEmptyLinesToKeep: 2
 KeepEmptyLinesAtTheStartOfBlocks: false
 
+SpaceBeforeCpp11BracedList: false
+Cpp11BracedListStyle: true