Use `page` query parameter instead of `p` to keep consistency with all URLs

Fix rubocop error

app/assets/javascripts/vue_pipelines_index/pipelines.js.es6

@@ -28,7 +28,7 @@ require('../vue_shared/components/pipelines_table');
     },
     props: ['scope', 'store', 'svgs'],
     created() {
-      const pagenum = gl.utils.getParameterByName('p');
+      const pagenum = gl.utils.getParameterByName('page');
       const scope = gl.utils.getParameterByName('scope');
       if (pagenum) this.pagenum = pagenum;
       if (scope) this.apiScope = scope;
@@ -36,7 +36,7 @@ require('../vue_shared/components/pipelines_table');
     },
     methods: {
       change(pagenum, apiScope) {
-        gl.utils.visitUrl(`?scope=${apiScope}&p=${pagenum}`);
+        gl.utils.visitUrl(`?scope=${apiScope}&page=${pagenum}`);
       },
     },
     template: `

spec/features/projects/pipelines/pipelines_spec.rb

@@ -277,6 +277,28 @@ describe 'Pipelines', :feature, :js do
           end
         end
       end
+
+      context 'with pagination' do
+        before do
+          create_list(:ci_empty_pipeline, 40, project: project)
+        end
+
+        it 'should render pagination' do
+          visit namespace_project_pipelines_path(project.namespace, project)
+          wait_for_vue_resource
+
+          expect(page).to have_css('.gl-pagination')
+          expect(page.find_all('tbody tr').length).to eq(20)
+        end
+
+        it "should render second page of pipelines" do
+          visit namespace_project_pipelines_path(project.namespace, project, page: '2')
+          wait_for_vue_resource
+
+          expect(page).to have_css('.gl-pagination')
+          expect(page.find_all('tbody tr').length).to eq(20)
+        end
+      end
     end
 
     describe 'POST /:project/pipelines' do