ci: fix AppVeyor install configuration

- Chocolatey dropped the 'cinst' shortname

Author: ralphlange

.appveyor.yml

@@ -45,9 +45,9 @@ skip_commits:
 
 install:
 # fetch submodules (like ci-scripts)
-  - cmd: git submodule update --init --recursive
+  - git submodule update --init --recursive
 # for the sequencer
-  - cinst re2c
+  - choco install re2c
 
 #---------------------------------#
 #   build matrix configuration    #

appveyor/.appveyor.yml.example-full

@@ -41,9 +41,9 @@ skip_commits:
 
 install:
 # fetch submodules (like ci-scripts)
-  - cmd: git submodule update --init --recursive
+  - git submodule update --init --recursive
 # for the sequencer
-  - cinst re2c
+  - choco install re2c
 
 #---------------------------------#
 #   build matrix configuration    #

appveyor/.appveyor.yml.example-mini

@@ -18,7 +18,7 @@ skip_commits:
     - '.travis.yml'
 
 install:
-  - cmd: git submodule update --init --recursive
+  - git submodule update --init --recursive
 
 image: Visual Studio 2022