[analyzer] Remove an unused enum value in RetainCountChecker.

No functional change intended.

Differential Revision: https://reviews.llvm.org/D27408

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@288917 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit d359c563265b82215f1e2db6ea6b96bef36ebbbe)
2 files changed