Changed 'Angular filters' link since old linked to site has been taken down (#773)

Author: juggledad

nodes/locales/en-US/ui_gauge.html

@@ -2,7 +2,7 @@
     <p>Adds a gauge type widget to the user interface.</p>
     <p>The <code>msg.payload</code> is searched for a numeric <i>value</i> and is formatted in accordance with
     the defined <b>Value Format</b>, which can then be formatted using
-    <a href="https://scotch.io/tutorials/all-about-the-built-in-angularjs-filters" target="_blank">Angular filters</a>.</p>
+    <a href="https://docs.angularjs.org/api/ng/filter" target="_blank">Angular filters</a>.</p>
     <p>For example : <code>{{value | number:1}}%</code> will round the value to one decimal place and append a % sign.</p>
     <p>The colours of each of 3 sectors can be specified and the gauge will blend between them.
     The colours should be specified in hex (#rrggbb) format.</p>