[tslint] remove '@theia/tslint' ext

Removes the `@theia/tslint` extension since it is
contributed by a builtin extension, and will no longer be
maintained by the project. The extension remains in the Git
history for anyone who would like to reference it or maintain
it.

Signed-off-by: Vincent Fugnitto <vincent.fugnitto@ericsson.com>

.travis.yml

@@ -51,7 +51,6 @@ cache:
     - packages/search-in-workspace/node_modules
     - packages/task/node_modules
     - packages/terminal/node_modules
-    - packages/tslint/node_modules
     - packages/typehierarchy/node_modules
     - packages/typescript/node_modules
     - packages/userstorage/node_modules

CHANGELOG.md

@@ -29,6 +29,8 @@ Breaking changes:
   - The extension will no longer be maintained by the project and remains in the Git history for anyone who would like to reference it or maintain it.
 - [textmate-grammars] removed the `@theia/textmate-grammars` extension [#6933](https://github.com/eclipse-theia/theia/pull/6933)
   - The extension will no longer be maintained by the project and remains in the Git history for anyone who would like to reference it or maintain it.
+- [tslint] removed the `@theia/tslint` extension [#6933](https://github.com/eclipse-theia/theia/pull/6933)
+  - The extension will no longer be maintained by the project and remains in the Git history for anyone who would like to reference it or maintain it.
 - [task] renamed method `getStrigifiedTaskSchema()` has been renamed to `getStringifiedTaskSchema()` [#6780](https://github.com/eclipse-theia/theia/pull/6780)
 - [task] renamed method `reorgnizeTasks()` has been renamed to `reorganizeTasks()` [#6780](https://github.com/eclipse-theia/theia/pull/6780)
 - Support VS Code icon and color theming. [#6475](https://github.com/eclipse-theia/theia/pull/6475)