.clang-tidy: correct style name is 'camelBack' not 'lowerCase'.

Summary: clang-tidy doesn't like to complain.

Differential Revision: https://reviews.llvm.org/D24413

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281370 91177308-0d34-0410-b5e6-96231b3b80d8

.clang-tidy

@@ -5,7 +5,7 @@ CheckOptions:
   - key:             readability-identifier-naming.EnumCase
     value:           CamelCase
   - key:             readability-identifier-naming.FunctionCase
-    value:           lowerCase
+    value:           camelBack
   - key:             readability-identifier-naming.MemberCase
     value:           CamelCase
   - key:             readability-identifier-naming.ParameterCase