Lowercased runner because it's referring to agent

We have guidelines for how we refer to runner vs GitLab Runner.
In this case, we mean the agent that runs the job, so it should
be lowercase. The style guide has details here:
https://docs.gitlab.com/ee/development/documentation/styleguide/word_list.html\#runner-runners

Changelog: changed

app/assets/javascripts/vue_shared/components/runner_instructions/runner_instructions.vue

@@ -13,7 +13,7 @@ export default {
   },
   modalId: 'runner-instructions-modal',
   i18n: {
-    buttonText: s__('Runners|Show Runner installation instructions'),
+    buttonText: s__('Runners|Show runner installation instructions'),
   },
   data() {
     return {

app/views/ci/runner/_how_to_setup_runner.html.haml

 - link = link_to _("Install GitLab Runner and ensure it's running."), 'https://docs.gitlab.com/runner/install/', target: '_blank', rel: 'noopener noreferrer'
 .gl-mb-3
-  %h5= _("Set up a %{type} Runner for a project") % { type: type }
+  %h5= _("Set up a %{type} runner for a project") % { type: type }
 %ol
   %li
     = link.html_safe

locale/gitlab.pot

@@ -30909,10 +30909,10 @@ msgstr ""
 msgid "Runners|Shared runners are available to every project in a GitLab instance. If you want a runner to build only specific projects, restrict the project in the table below. After you restrict a runner to a project, you cannot change it back to a shared runner."
 msgstr ""
 
-msgid "Runners|Show Runner installation instructions"
+msgid "Runners|Show runner installation and registration instructions"
 msgstr ""
 
-msgid "Runners|Show runner installation and registration instructions"
+msgid "Runners|Show runner installation instructions"
 msgstr ""
 
 msgid "Runners|Something went wrong while fetching runner data."
@@ -32743,7 +32743,7 @@ msgstr ""
 msgid "Set up Jira Integration"
 msgstr ""
 
-msgid "Set up a %{type} Runner for a project"
+msgid "Set up a %{type} runner for a project"
 msgstr ""
 
 msgid "Set up a hardware device as a second factor to sign in."

spec/frontend/vue_shared/components/runner_instructions/runner_instructions_spec.js

@@ -22,9 +22,9 @@ describe('RunnerInstructions component', () => {
     wrapper.destroy();
   });
 
-  it('should show the "Show Runner installation instructions" button', () => {
+  it('should show the "Show runner installation instructions" button', () => {
     expect(findModalButton().exists()).toBe(true);
-    expect(findModalButton().text()).toBe('Show Runner installation instructions');
+    expect(findModalButton().text()).toBe('Show runner installation instructions');
   });
 
   it('should not render the modal once mounted', () => {