feat(fvm): update to use flutter version datasource (#15765)

lib/modules/manager/fvm/extract.spec.ts

@@ -31,7 +31,7 @@ describe('modules/manager/fvm/extract', () => {
       expect(res.deps).toEqual([
         {
           currentValue: '2.10.1',
-          datasource: 'github-tags',
+          datasource: 'flutter-version',
           depName: 'flutter',
           packageName: 'flutter/flutter',
         },
@@ -46,7 +46,7 @@ describe('modules/manager/fvm/extract', () => {
       expect(res.deps).toEqual([
         {
           currentValue: 'stable',
-          datasource: 'github-tags',
+          datasource: 'flutter-version',
           depName: 'flutter',
           packageName: 'flutter/flutter',
         },

lib/modules/manager/fvm/extract.ts

 import is from '@sindresorhus/is';
 import { logger } from '../../../logger';
-import { GithubTagsDatasource } from '../../datasource/github-tags';
+import { FlutterVersionDatasource } from '../../datasource/flutter-version';
 import type { PackageDependency, PackageFile } from '../types';
 
 interface FvmConfig {
@@ -33,7 +33,7 @@ export function extractPackageFile(
   const dep: PackageDependency = {
     depName: 'flutter',
     currentValue: fvmConfig.flutterSdkVersion,
-    datasource: GithubTagsDatasource.id,
+    datasource: FlutterVersionDatasource.id,
     packageName: 'flutter/flutter',
   };
   return { deps: [dep] };

lib/modules/manager/fvm/index.ts

-import { GithubTagsDatasource } from '../../datasource/github-tags';
+import { FlutterVersionDatasource } from '../../datasource/flutter-version';
 import * as semverVersioning from '../../versioning/semver';
 
 export { extractPackageFile } from './extract';
 
-export const supportedDatasources = [GithubTagsDatasource.id];
+export const supportedDatasources = [FlutterVersionDatasource.id];
 
 export const defaultConfig = {
   fileMatch: ['(^|\\/)\\.fvm\\/fvm_config\\.json$'],