Fixing typo

Author: clanmills

mingw.yml

@@ -43,7 +43,7 @@ build_script:
     - cmd: set   CMD=%CMD%; cmake --build . --config Release
     - cmd: rem echo %CMD%
     - cd %APPVEYOR_BUILD_FOLDER%
-    - cmd: if "%BUILD%"=="MINGW64" then C:\msys64\usr\bin\bash -c "%CMD%"
+    - cmd: if "%BUILD%"=="MINGW64" C:\msys64\usr\bin\bash -c "%CMD%"
     - cmd: set   CMD=which python3 python
     - cmd: set   CMD=%CMD%; python --version
     - cmd: set   CMD=%CMD%; build/bin/exiv2 --verbose --version; pwd ; ls -l