Restore `+2` when reserve space for vector. #75

Job	Run time
CMake test (with abseil)	6m 34s
CMake clang 14 (maintainer mode, abiv2)	17m 14s
CMake clang 14 (maintainer mode, async)	17m 47s
CMake gcc 12 (maintainer mode, async)	10m 48s
CMake clang 14 (maintainer mode, sync)	16m 47s
CMake gcc 12 (maintainer mode, sync)	11m 2s
CMake msvc (maintainer mode)	15m 10s
CMake test (with opentracing-shim)	6m 21s
CMake test (without otlp-exporter)	8m 35s
CMake C++14 test(GCC)	5m 56s
CMake C++20 test(GCC)	11m 31s
CMake test (without otlp-exporter and with async export)	7m 1s
Bazel asan config	11m 8s
Bazel noexcept	6m 37s
Bazel nortti	9m 13s
Bazel on MacOS	11m 3s
Bazel	17m 22s
Bazel with async export	8m 30s
Bazel tsan config	8m 6s
Bazel valgrind	10m 32s
Bazel with external abseil	7m 43s
Benchmark	3m 32s
CMake do not install test (with otlp-exporter)	21m 21s
CMake install test (with abseil)	6m 27s
CMake test (with modern protobuf,grpc and abseil)	26m 55s
CMake test (build shared libraries with otlp-exporter and static gRPC)	21m 24s
CMake test (with otlp-exporter)	20m 31s
CMake C++17 test(GCC)	8m 39s
CMake C++20 test(Clang with libc++)	13m 33s
Copyright	8s
Format	22s
CMake -> exporter proto	17m 4s
Bazel Windows	34m 25s
Plugin -> CMake	1m 32s
CMake (With async export) -> exporter proto	19m 44s
CMake -> exporter proto (Build as DLL)	17m 54s
DocFX check	1m 14s
Code coverage	16m 39s
markdown-lint	7s
misspell	6s
Plugin -> CMake Windows	10m 5s
	7h 46m 42s

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