plantuml: minor clean up

This commit removes the unnecessary check on `spacemacs-indent-sensitive-modes` variable,
which is defined in `spacemacs-default` layer.

layers/+lang/plantuml/packages.el

@@ -44,11 +44,10 @@
     (progn
       ;; Our default is jar execution, not server as server is not working reliable see #13574
       (setq plantuml-default-exec-mode 'jar)
-      (when (boundp 'spacemacs-indent-sensitive-modes)
-        ;; for now plantuml electric indentation is buggy and does not
-        ;; really work, let's disable auto-indentation on paste for
-        ;; this mode
-        (add-to-list 'spacemacs-indent-sensitive-modes 'plantuml-mode))
+      ;; for now plantuml electric indentation is buggy and does not
+      ;; really work, let's disable auto-indentation on paste for
+      ;; this mode
+      (add-to-list 'spacemacs-indent-sensitive-modes 'plantuml-mode)
       (spacemacs/declare-prefix-for-mode 'plantuml-mode
         "mc" "compile")
       (spacemacs/set-leader-keys-for-major-mode 'plantuml-mode