[typescript-angular] drop support of angular below 6.0.0 (#6360)

* typescript-angular: drop support for angular below 6.0.0

* typescript-angular: re-generate samples

* typescript-angular: re-generate docs

Author: macjohnny

bin/typescript-angular-petstore-all.sh

@@ -1,10 +1,5 @@
 #!/bin/sh
 
-./bin/typescript-angular-v2-petstore.sh
-./bin/typescript-angular-v2-petstore-with-npm.sh
-./bin/typescript-angular-v2-petstore-interfaces.sh
-./bin/typescript-angular-v4-petstore-with-npm.sh
-./bin/typescript-angular-v4.3-petstore-with-npm.sh
 ./bin/typescript-angular-v6-petstore-not-provided-in-root.sh
 ./bin/typescript-angular-v6-petstore-not-provided-in-root-with-npm.sh
 ./bin/typescript-angular-v6-petstore-provided-in-root.sh

bin/typescript-angular-v2-petstore-interfaces.sh

@@ -1,8 +1,3 @@
-call .\bin\windows\typescript-angular-v2-with-npm.bat
-call .\bin\windows\typescript-angular-v2-interfaces.bat
-call .\bin\windows\typescript-angular-v2.bat
-call .\bin\windows\typescript-angular-v4-with-npm.bat
-call .\bin\windows\typescript-angular-v4.3-with-npm.bat
 call .\bin\windows\typescript-angular-v6-provided-in-root.bat
 call .\bin\windows\typescript-angular-v6-provided-in-root-with-npm.bat
 call .\bin\windows\typescript-angular-v6-not-provided-in-root.bat

bin/typescript-angular-v2-petstore-with-npm.sh

@@ -15,7 +15,7 @@ sidebar_label: typescript-angular
 |modelFileSuffix|The suffix of the file of the generated model (model<suffix>.ts).| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |modelSuffix|The suffix of the generated model.| |null|
-|ngVersion|The version of Angular.| |9.0.0|
+|ngVersion|The version of Angular. (At least 6.0.0)| |9.0.0|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
 |npmVersion|The version of your npm package. If not provided, using the version from the OpenAPI specification file.| |1.0.0|