chore(deps): update https://github.com/microsoft/vcpkg digest to 81e3c88 #574

Job	Run time
pre-commit	23s
check • x64-linux • gcc-14 • c++20 • Debug	3m 51s
check • x64-linux • llvm-18 • c++20 • RelWithDebInfo	3m 34s
check • x64-linux • gcc-14 • c++20 • RelWithDebInfo	3m 40s
check • x64-linux • llvm-18 • c++20 • Debug	3m 4s
check • sanitizers • address,undefined • RelWithDebInfo	3m 7s
check • sanitizers • address,undefined • Debug	3m 29s
check • x64-windows • msvc-2022 • c++20 • RelWithDebInfo	3m 14s
check • x64-windows • llvm-18 • c++20 • RelWithDebInfo	3m 27s
check • x64-windows • llvm-18 • c++20 • Debug	38s
cppcheck	3m 55s
check • x64-windows • msvc-2022 • c++20 • Debug	1s
check • ${{ matrix.triplet }} • ${{ matrix.compiler }} • c++${{ matrix.std }} • ${{ matrix.build_type }}	0s
check • valgrind • RelWithDebInfo	4m 46s
check • valgrind • Debug	3m 55s
check • x64-mingw-dynamic • mingw • c++20 • Debug	5m 5s
check-docs	4m 2s
check • x64-mingw-dynamic • mingw • c++20 • RelWithDebInfo	8m 35s
clang-tidy	2m 18s
codecov	3m 3s
pass	4s
	1h 4m 11s

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