Remove duplicate install command in CMakeLists.txt for api #8978

Job	Run time
Bazel noexcept	11m 55s
Bazel asan config	14m 54s
Bazel nortti	12m 14s
Bazel	12m 6s
Bazel on MacOS	19m 4s
Bazel with async export	12m 6s
Bazel tsan config	13m 11s
Bazel valgrind	14m 51s
Bazel with external abseil	12m 27s
Benchmark	7m 47s
CMake test (with abseil)	4m 38s
CMake clang 14 (maintainer mode, abiv2)	14m 28s
CMake clang 14 (maintainer mode, async)	14m 1s
CMake clang 14 (maintainer mode, sync)	13m 52s
CMake do not install test (with otlp-exporter)	15m 18s
CMake gcc 12 (maintainer mode, async)	8m 25s
CMake gcc 12 (maintainer mode, sync)	8m 2s
CMake install test (with abseil)	4m 19s
CMake test (with modern protobuf,grpc and abseil)	17m 51s
CMake msvc (maintainer mode)	7m 23s
CMake msvc (maintainer mode) with C++20	9m 14s
CMake test (with opentracing-shim)	4m 23s
CMake test (build shared libraries with otlp-exporter and static gRPC)	14m 58s
CMake test (with otlp-exporter)	15m 16s
CMake test (without otlp-exporter)	5m 27s
CMake C++14 test(GCC)	4m 21s
CMake C++17 test(GCC)	6m 19s
CMake C++20 test(Clang with libc++)	10m 1s
CMake C++20 test(GCC)	10m 7s
CMake test (without otlp-exporter and with async export)	4m 52s
Code coverage	11m 20s
Copyright	6s
DocFX check	1m 14s
Format	12s
markdown-lint	7s
misspell	7s
Plugin -> CMake	48s
CMake -> exporter proto	11m 47s
Bazel Windows	19m 0s
Plugin -> CMake Windows	6m 1s
CMake (With async export) -> exporter proto	12m 14s
CMake -> exporter proto (Build as DLL)	12m 36s
	6h 39m 22s

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