Revert "Change OTLP HTTP content_type default to binary" #9253

Job	Run time
CMake clang 15 (maintainer mode, async)	15m 33s
CMake clang 15 (maintainer mode, sync)	14m 24s
CMake gcc 13 (maintainer mode, sync)	9m 23s
CMake test (without otlp-exporter)	5m 13s
CMake test (with abseil)	5m 1s
CMake clang 15 (maintainer mode, abiv2)	18m 1s
CMake gcc 13 (maintainer mode, async)	7m 19s
CMake msvc (maintainer mode)	7m 54s
CMake msvc (maintainer mode) with C++20	9m 22s
CMake test (with opentracing-shim)	6m 3s
CMake C++14 test(GCC)	6m 42s
CMake C++17 test(GCC)	4m 45s
CMake C++20 test(Clang with libc++)	9m 57s
CMake C++20 test(GCC)	8m 45s
CMake test (without otlp-exporter and with async export)	5m 14s
Bazel noexcept	11m 43s
Bazel	12m 30s
Bazel with async export	12m 55s
Bazel with external abseil	13m 3s
CMake do not install test (with otlp-exporter)	14m 22s
Bazel valgrind	13m 40s
CMake install test (with abseil)	4m 53s
CMake test (with modern protobuf,grpc and abseil)	19m 8s
CMake test (build shared libraries with otlp-exporter and static gRPC)	13m 36s
CMake test (with otlp-exporter)	14m 24s
CMake C++23 test(GCC)	10m 27s
CMake C++23 test(Clang with libc++)	11m 27s
Plugin -> CMake	1m 16s
Bazel asan config	15m 11s
Bazel nortti	13m 27s
Bazel on MacOS	14m 9s
Bazel tsan config	13m 14s
Benchmark	7m 57s
Code coverage	12m 55s
Copyright	4s
Format	42s
markdown-lint	11s
misspell	4s
CMake -> exporter proto	12m 20s
Bazel Windows	18m 45s
Plugin -> CMake Windows	6m 49s
CMake (With async export) -> exporter proto	12m 9s
CMake -> exporter proto (Build as DLL)	23m 20s
DocFX check	54s
	7h 19m 11s

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