Refactored routes hash to be a "single" value

refs https://linear.app/tryghost/issue/CORE-35/refactor-route-and-redirect-settings

- It's a continuation of simplifying the concept of multiple frontend settings. If there's just one file we support there should be just one hash

core/frontend/services/settings/index.js

@@ -4,11 +4,9 @@ const SettingsLoader = require('./loader');
 const ensureSettingsFile = require('./ensure-settings');
 
 /**
- * md5 hashes of default settings
+ * md5 hashes of default routes settings
  */
-const defaultHashes = {
-    routes: '3d180d52c663d173a6be791ef411ed01'
-};
+const defaultRoutesSettingHash = '3d180d52c663d173a6be791ef411ed01';
 
 const calculateHash = (data) => {
     return crypto.createHash('md5')
@@ -36,8 +34,8 @@ module.exports = {
         return SettingsLoader('routes');
     },
 
-    getDefaulHash: (setting) => {
-        return defaultHashes[setting];
+    getDefaultHash: () => {
+        return defaultRoutesSettingHash;
     },
 
     getCurrentHash: async (setting) => {

test/unit/data/schema/integrity.test.js

@@ -64,6 +64,6 @@ describe('DB version integrity', function () {
         fixturesHash.should.eql(currentFixturesHash);
         settingsHash.should.eql(currentSettingsHash);
         routesHash.should.eql(currentRoutesHash);
-        routesHash.should.eql(frontendSettings.getDefaulHash('routes'));
+        routesHash.should.eql(frontendSettings.getDefaultHash());
     });
 });