tools: update glob-parent to 5.1.2

In the markdown linting rollup script, update glob-parent to 5.1.2.

As of this writing, the Snyk advisory incorrectly states that all
versions are vulnerable. 5.1.2 was released today with the fix.

Refs: https://app.snyk.io/vuln/SNYK-JS-GLOBPARENT-1016905

tools/lint-md.js

@@ -21005,14 +21005,15 @@ var isWin32 = os__default['default'].platform() === 'win32';
 
 var slash = '/';
 var backslash = /\\/g;
-var enclosure = /[\{\[].*[\/]*.*[\}\]]$/;
+var enclosure = /[\{\[].*[\}\]]$/;
 var globby = /(^|[^\\])([\{\[]|\([^\)]+$)/;
 var escaped = /\\([\!\*\?\|\[\]\(\)\{\}])/g;
 
 /**
  * @param {string} str
  * @param {Object} opts
  * @param {boolean} [opts.flipBackslashes=true]
+ * @returns {string}
  */
 var globParent = function globParent(str, opts) {
   var options = Object.assign({ flipBackslashes: true }, opts);