Remove .es6 from file extensions (!9241)

app/assets/javascripts/abuse_reports.js

app/assets/javascripts/activities.js

app/assets/javascripts/blob/blob_ci_yaml.js

app/assets/javascripts/blob/blob_dockerfile_selector.js

app/assets/javascripts/blob/blob_dockerfile_selectors.js

app/assets/javascripts/blob/blob_license_selectors.js

app/assets/javascripts/blob/template_selector.js

app/assets/javascripts/boards/boards_bundle.js

app/assets/javascripts/boards/components/board.js

...assets/javascripts/boards/components/board_blank_state.js

app/assets/javascripts/boards/components/board_delete.js

app/assets/javascripts/boards/components/board_list.js

app/assets/javascripts/boards/components/board_sidebar.js

app/assets/javascripts/boards/components/issue_card_inner.js

...assets/javascripts/boards/components/modal/empty_state.js

app/assets/javascripts/boards/components/modal/filters.js

...sets/javascripts/boards/components/modal/filters/label.js

.../javascripts/boards/components/modal/filters/milestone.js

...ssets/javascripts/boards/components/modal/filters/user.js

app/assets/javascripts/boards/components/modal/footer.js