ui: Replace block comments with line comments

eslint expects comments that look like:

/**
 * foo
 * bar
 * baz
 */
somecode;

to be valid esdoc, which we don't do so it complains fix this by
converting all multiline block comments (/* */) to single line comments:

// foo
// bar
// baz
somecode;

Which we use more in any case so this just helps us be consistent.

Change-Id: Ib2e7dbb68be2eedea1be2fd36a62f62ef7b889c2