fix(techdocs): support dompurify 3.2.6

Element.tagName is uppercased, see https://developer.mozilla.org/fr/docs/Web/API/Element/tagName

Signed-off-by: Gabriel Dugny <gabriel.dugny@believe.com>

.changeset/stupid-areas-share.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-techdocs': patch
+---
+
+Support Techdocs redirect with dompurify 3.2.6+

plugins/techdocs/src/reader/transformers/html/transformer.ts

@@ -65,7 +65,7 @@ export const useSanitizerTransformer = (): Transformer => {
 
       // Only allow http-equiv and content attributes on meta tags. They are required for the redirect feature.
       DOMPurify.addHook('uponSanitizeAttribute', (currNode, data) => {
-        if (currNode.tagName !== 'meta') {
+        if (currNode.tagName !== 'META') {
           if (data.attrName === 'http-equiv' || data.attrName === 'content') {
             currNode.removeAttribute(data.attrName);
           }