Remove reference to outdated issue in comments

This commit removes a reference to an outdated issue from comments
within vuex-action files.

It pointed to an issue that aimed to make the default export obsolete,
but the issue has been closed and the export will be needed until
all tests have been migrated to karma.

See comment on the issue:
https://gitlab.com/gitlab-org/gitlab/issues/24511#note_273343173

ee/app/assets/javascripts/security_dashboard/store/modules/filters/actions.js

@@ -47,5 +47,4 @@ export const setToggleValue = ({ commit }, { key, value }) => {
 };
 
 // prevent babel-plugin-rewire from generating an invalid default during karma tests
-// This is no longer needed after gitlab-foss#52179 is merged
 export default () => {};

ee/app/assets/javascripts/security_dashboard/store/modules/filters/getters.js

@@ -41,5 +41,4 @@ export const activeFilters = state => {
 export const visibleFilters = ({ filters }) => filters.filter(({ hidden }) => !hidden);
 
 // prevent babel-plugin-rewire from generating an invalid default during karma tests
-// This is no longer needed after gitlab-foss#52179 is merged
 export default () => {};

ee/app/assets/javascripts/security_dashboard/store/modules/projects/actions.js

@@ -56,5 +56,4 @@ export const receiveProjectsError = ({ commit }) => {
 };
 
 // prevent babel-plugin-rewire from generating an invalid default during karma tests
-// This is no longer needed after gitlab-foss#52179 is merged
 export default () => {};

ee/app/assets/javascripts/security_dashboard/store/modules/vulnerabilities/actions.js

@@ -480,5 +480,4 @@ export const closeDismissalCommentBox = ({ commit }) => {
 };
 
 // prevent babel-plugin-rewire from generating an invalid default during karma tests
-// This is no longer needed after gitlab-foss#52179 is merged
 export default () => {};

ee/app/assets/javascripts/security_dashboard/store/modules/vulnerable_projects/actions.js

@@ -40,5 +40,4 @@ export const receiveProjectsError = ({ commit }) => {
 };
 
 // prevent babel-plugin-rewire from generating an invalid default during karma tests
-// This is no longer needed after gitlab-foss#52179 is merged
 export default () => {};

ee/app/assets/javascripts/security_dashboard/store/modules/vulnerable_projects/getters.js

@@ -15,5 +15,4 @@ export const severityGroups = ({ projects }) => {
 };
 
 // prevent babel-plugin-rewire from generating an invalid default during karma tests
-// This is no longer needed after gitlab-foss#52179 is merged
 export default () => {};