Update learn/os_setup/install_gfortran.md

Co-authored-by: Laurence Kedward <[email protected]>

Author: smeskos

learn/os_setup/install_gfortran.md

@@ -13,7 +13,7 @@ Three sources provide quick and easy way to install GFortran compiler on Windows
 1. [http://www.equation.com](http://www.equation.com/servlet/equation.cmd?fa=fortran), provides 32 and 64-bit x86
  executables of the latest (10.2) gcc-version.
 2. [TDM GCC](https://jmeubank.github.io/tdm-gcc/articles/2020-03/9.2.0-release), provides 32 and 64-bit x86 executables of the 9.2 gcc-version.
-3. [MinGW-w64](http://mingw-w64.org/doku.php/download/mingw-builds) provides a 64-bit x86 executable of the 7.2 gcc-version.
+3. [MinGW-w64](http://mingw-w64.org/doku.php/download/mingw-builds) provides a 64-bit x86 executable of the 8.1.0 gcc-version.
 
 In all the above choices, the process is straightforward—just download the installer and follow the installation wizard.