shell: exec encoding is utf8 by default and no shell

explicitly mark calls that require the shell

src/database.js

@@ -144,7 +144,7 @@ async function exportToFile(file) {
     assert.strictEqual(typeof file, 'string');
 
     // latest mysqldump enables column stats by default which is not present in 5.7 util
-    const mysqlDumpHelp = await shell.promises.exec('exportToFile', '/usr/bin/mysqldump --help', { encoding: 'utf8' });
+    const mysqlDumpHelp = await shell.promises.exec('exportToFile', '/usr/bin/mysqldump --help', {});
     const hasColStats = mysqlDumpHelp.includes('column-statistics');
     const colStats = hasColStats ? '--column-statistics=0' : '';