[cmake] Delete redundant install command for clang-refactor.

[cmake] Delete redundant install command for clang-refactor.

Summary: Install targets for clang tools are controlled by
CLANG_BUILD_TOOLS, and when OFF, cmake issues the following warning:

WARNING: Target "clang-refactor" has EXCLUDE_FROM_ALL set and will not
be built by default but an install rule has been provided for it.
CMake does not define behavior for this case.

Differential Revision: https://reviews.llvm.org/D41807

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@322147 91177308-0d34-0410-b5e6-96231b3b80d8