Remove invalid content

Remove broken link to single header version and reference to vcpkg
package.

Author: lpinca

README.md

@@ -30,7 +30,7 @@ Requirements
 
 - C++11 compatible compiler. We support LLVM clang, GCC, Visual Studio. (Our optional benchmark tool requires C++17.)
 - For high speed, you should have a recent 64-bit system (e.g., ARM or x64).
-- If you rely on CMake, you should use a recent CMake (at least 3.15) ; otherwise you may use the [single header version](#single-header-version). The library is also available from Microsoft's vcpkg.
+- If you rely on CMake, you should use a recent CMake (at least 3.15).
 - AVX-512 support require a processor with AVX512-VBMI2 (Ice Lake or better) and a recent compiler (GCC 8 or better, Visual Studio 2019 or better, LLVM clang 6 or better). You need a correspondingly recent assembler such as gas (2.30+) or nasm (2.14+): recent compilers usually come with recent assemblers. If you mix a recent compiler with an incompatible/old assembler (e.g., when using a recent compiler with an old Linux distribution), you may get errors at build time because the compiler produces instructions that the assembler does not recognize: you should update your assembler to match your compiler (e.g., upgrade binutils to version 2.30 or better under Linux) or use an older compiler matching the capabilities of your assembler. 
 
 ## Reference