Update CI

Author: jeking3

.appveyor.yml

@@ -65,10 +65,6 @@ environment:
       B2_CXXSTD: 14,17
       B2_TOOLSET: msvc-14.1
 
-    - FLAVOR: Visual Studio 2015, 2013
-      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
-      B2_TOOLSET: msvc-12.0,msvc-14.0
-
     - FLAVOR: cygwin (32-bit)
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
       ADDPATH: C:\cygwin\bin;
@@ -83,20 +79,6 @@ environment:
       B2_CXXSTD: 03,11,14,1z
       B2_TOOLSET: gcc
 
-    - FLAVOR: mingw32
-      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
-      B2_ADDRESS_MODEL: 32
-      ADDPATH: C:\mingw\bin;
-      B2_CXXSTD: 03,11,14,1z
-      B2_TOOLSET: gcc
-
-    - FLAVOR: mingw64
-      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
-      ADDPATH: C:\mingw-w64\x86_64-8.1.0-posix-seh-rt_v6-rev0\mingw64\bin;
-      B2_ADDRESS_MODEL: 64
-      B2_CXXSTD: 03,11,14,17,2a
-      B2_TOOLSET: gcc
-
 install:
   - git clone --depth 1 https://github.com/boostorg/boost-ci.git C:\boost-ci-cloned
   # Copy ci folder if not testing Boost.CI