Allow for different shakapacker versions in convert script

Author: alexeyr

script/convert

@@ -13,13 +13,13 @@ new_config = File.expand_path("../spec/dummy/config/webpacker.yml", __dir__)
 
 File.rename(old_config, new_config)
 
-gsub_file_content("../Gemfile.development_dependencies", 'gem "shakapacker", "8.0.0"', 'gem "shakapacker", "6.6.0"')
+gsub_file_content("../Gemfile.development_dependencies", /gem "shakapacker", "[^"]*"/, 'gem "shakapacker", "6.6.0"')
 
 # The below packages don't work on the oldest supported Node version and aren't needed there anyway
 gsub_file_content("../package.json", /"knip": "[^"]*",/, "")
 gsub_file_content("../package.json", %r{"@arethetypeswrong/cli": "[^"]*",}, "")
 
-gsub_file_content("../spec/dummy/package.json", '"shakapacker": "8.0.0",', '"shakapacker": "6.6.0",')
+gsub_file_content("../spec/dummy/package.json", /"shakapacker": "[^"]*",/, '"shakapacker": "6.6.0",')
 
 gsub_file_content("../spec/dummy/config/webpack/commonWebpackConfig.js", /generateWebpackConfig(\(\))?/,
                   "webpackConfig")