fix the version fix for 5.6.0-RC1

* look for number instead of string

lib/antora/extensions/version-fix.js

@@ -4,7 +4,7 @@ module.exports.register = function () {
   this.once('contentAggregated', ({ contentAggregate }) => {
     contentAggregate.forEach((componentVersionBucket) => {
       if (componentVersionBucket.prerelease === 'true') componentVersionBucket.prerelease = true
-      if (!componentVersionBucket.name && componentVersionBucket.displayVersion === '5.6') {
+      if (!componentVersionBucket.name && componentVersionBucket.displayVersion === 5.6) {
         componentVersionBucket.name = 'ROOT'
         componentVersionBucket.version = '5.6.0-RC1'
         delete componentVersionBucket.displayVersion