Fix mingw link typo in README.md

Author: Wuvist

README.md

@@ -409,7 +409,7 @@ In order to build and install OpenCV 4.10.0 on Windows, you must first download
 
 #### MinGW-W64
 
-Download and run the MinGW-W64 compiler installer from [https://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win32/Personal%20Builds/mingw-builds/8.1.0/](https://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win32/Personal%20Builds/mingw-builds/8.1.0/).
+Download and run the MinGW-W64 compiler installer from [https://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win64/Personal%20Builds/mingw-builds/8.1.0/](https://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win64/Personal%20Builds/mingw-builds/8.1.0/).
 
 The latest version of the MinGW-W64 toolchain is `8.1.0`, but any version from `8.X` on should work.