refactor: releaseDate -> releaseTimestamp

lib/datasource/common.ts

@@ -19,7 +19,6 @@ export interface Release {
   gitref?: string;
   isDeprecated?: boolean;
 
-  releaseDate?: string;
   releaseTimestamp?: any;
   version: string;
 }

lib/datasource/ruby-version/index.ts

@@ -37,11 +37,11 @@ export async function getPkgReleases(
       if (columns.length) {
         const version = columns[0].replace('Ruby ', '');
         if (isVersion(version)) {
-          const releaseDate = columns[1];
+          const releaseTimestamp = columns[1];
           const changelogUrl = columns[2]
             .replace('<a href="', 'https://www.ruby-lang.org')
             .replace('">more...</a>', '');
-          res.releases.push({ version, releaseDate, changelogUrl });
+          res.releases.push({ version, releaseTimestamp, changelogUrl });
         }
       }
     }

lib/datasource/rubygems/get.ts

@@ -81,13 +81,13 @@ export const getDependency = async ({
       ({
         number: version,
         platform: rubyPlatform,
-        created_at: releaseDate,
+        created_at: releaseTimestamp,
         rubygems_version: rubygemsVersion,
         ruby_version: rubyVersion,
       }) => ({
         version,
         rubyPlatform,
-        releaseDate,
+        releaseTimestamp,
         rubygemsVersion,
         rubyVersion,
       })