Fixed content-length in labs snapshot

refs: 22fd7f289c

- in the mentioned commit I changed the tests so that we don't need to update snapshots for every labs flag change
- this commit does the same for content-length which didn't get picked up locally, but does on CI for some reason
- the goal is to allow the team to add and remove flags without needing to update a random snapshot

ghost/core/test/e2e-api/admin/__snapshots__/settings.test.js.snap

@@ -280,7 +280,7 @@ exports[`Settings API Browse Can request all settings 2: [headers] 1`] = `
 Object {
   "access-control-allow-origin": "http://127.0.0.1:2369",
   "cache-control": "no-cache, private, no-store, must-revalidate, max-stale=0, post-check=0, pre-check=0",
-  "content-length": "3452",
+  "content-length": StringMatching /\\\\d\\+/,
   "content-type": "application/json; charset=utf-8",
   "etag": StringMatching /\\(\\?:W\\\\/\\)\\?"\\(\\?:\\[ !#-\\\\x7E\\\\x80-\\\\xFF\\]\\*\\|\\\\r\\\\n\\[\\\\t \\]\\|\\\\\\\\\\.\\)\\*"/,
   "vary": "Origin, Accept-Encoding",

ghost/core/test/e2e-api/admin/settings.test.js

@@ -3,7 +3,7 @@ const SingleUseTokenProvider = require('../../../core/server/services/members/Si
 const settingsService = require('../../../core/server/services/settings/settings-service');
 const settingsCache = require('../../../core/shared/settings-cache');
 const {agentProvider, fixtureManager, mockManager, matchers} = require('../../utils/e2e-framework');
-const {stringMatching, anyEtag, anyUuid} = matchers;
+const {stringMatching, anyEtag, anyUuid, anyStringNumber} = matchers;
 const models = require('../../../core/server/models');
 const {anyErrorId} = matchers;
 
@@ -63,7 +63,9 @@ describe('Settings API', function () {
                     settings: matchSettingsArray(CURRENT_SETTINGS_COUNT)
                 })
                 .matchHeaderSnapshot({
-                    etag: anyEtag
+                    etag: anyEtag,
+                    // Special rule for this test, as the labs setting changes a lot
+                    'content-length': anyStringNumber
                 });
         });