use latest techdocs docker image by default

Signed-off-by: Morgan Bentell <mbentell@spotify.com>

.changeset/heavy-ravens-fold.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-techdocs-node': patch
+---
+
+Use latest techdocs docker image by default. The latest image contains security updates.

plugins/techdocs-node/src/stages/generate/techdocs.ts

@@ -53,7 +53,7 @@ export class TechdocsGenerator implements GeneratorBase {
    * The default docker image (and version) used to generate content. Public
    * and static so that techdocs-node consumers can use the same version.
    */
-  public static readonly defaultDockerImage = 'spotify/techdocs:v1.2.0';
+  public static readonly defaultDockerImage = 'spotify/techdocs:v1.2.1';
   private readonly logger: Logger;
   private readonly containerRunner?: ContainerRunner;
   private readonly options: GeneratorConfig;