Use new @jsonhpp//:singleheader-json also available in 3.11.3.bcr.1 #4726

Job	Run time
ClangTidy	3m 24s
RunBantBuildCleaner	3m 20s
KytheVerification	0s
MacOsBuild	4m 10s
x86_64 test	3m 37s
MacOsBuildDevTools	4m 10s
arm64 test	4m 30s
VerifyFormatting	25s
x86_64 test-clang	3m 47s
arm64 test-clang	4m 16s
KytheXrefs	0s
x86_64 test-nortti	3m 21s
x86_64 test-c++20	3m 36s
x86_64 test-c++23	3m 27s
PrepareVSPlugin	2m 31s
x86_64 smoke-test	9m 58s
arm64 smoke-test	12m 5s
x86_64 asan	5m 39s
WindowsBuild	9m 48s
x86_64 asan-clang	5m 4s
x86_64 compile	3m 20s
arm64 compile	3m 43s
x86_64 compile-clang	3m 4s
arm64 compile-clang	3m 41s
x86_64 compile-static	3m 46s
arm64 compile-static	3m 57s
x86_64 compile-static-clang	3m 43s
arm64 compile-static-clang	3m 38s
x86_64 coverage	18m 45s
x86_64 clean	7m 39s
arm64 clean	7m 19s
Build and deploy GitHub pages	11s
📦 Release	0s
	2h 29m 54s

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