code: public void deleteVariable(Object projectIdOrPath, String key) throws GitLabApiException {
          delete(Response.Status.NO_CONTENT, null, "projects", getProjectIdOrPath(projectIdOrPath), "variables", key);
      }
docs: Deletes a project variable.
  
  <pre><code>DELETE /projects/:id/variables/:key</code></pre>
  
  @param projectIdOrPath projectIdOrPath the project in the form of an Integer(ID), String(path), or Project instance, required
  @param key the key of an existing variable, required
  @throws GitLabApiException if any exception occurs