Have embark-{next,previous}-symbol act on symbol at point

The old way, which prompted for a symbol, was very similar to existing
commands like isearch-forward-symbol or word-search-forward; and in
particular I couldn't really imagine anyone wanting to use the embark
versions directly (i.e., not through embark-act) given the existence
of isearch-forward-symbol, which even has a default binding. But these
new versions that act on the symbol at point are something you might
actually want to bind directly. And for the usage as actions they work
exactly as before.

embark.el

@@ -3624,25 +3624,29 @@ minibuffer, which means it can be used as an Embark action."
         (unhighlight-regexp regexp)
       (highlight-symbol-at-point))))
 
-(defun embark-next-symbol (symbol)
-  "Jump to next occurrence of SYMBOL.
+(defun embark-next-symbol ()
+  "Jump to next occurrence of symbol at point.
 The search respects symbol boundaries."
-  (interactive "sSymbol: ")
-  (let ((regexp (format "\\_<%s\\_>" (regexp-quote symbol))))
-    (when (looking-at regexp)
-      (forward-symbol 1))
-    (unless (re-search-forward regexp nil t)
-      (user-error "Symbol `%s' not found" symbol))))
-
-(defun embark-previous-symbol (symbol)
-  "Jump to previous occurrence SYMBOL.
+  (interactive)
+  (if-let ((symbol (thing-at-point 'symbol)))
+      (let ((regexp (format "\\_<%s\\_>" (regexp-quote symbol))))
+        (when (looking-at regexp)
+          (forward-symbol 1))
+        (unless (re-search-forward regexp nil t)
+          (user-error "Symbol `%s' not found" symbol)))
+    (user-error "No symbol at point")))
+
+(defun embark-previous-symbol ()
+  "Jump to previous occurrence of symbol at point.
 The search respects symbol boundaries."
-  (interactive "sSymbol: ")
-  (let ((regexp (format "\\_<%s\\_>" (regexp-quote symbol))))
-    (when (looking-back regexp (- (point) (length symbol)))
-      (forward-symbol -1))
-    (unless (re-search-backward regexp nil t)
-      (user-error "Symbol `%s' not found" symbol))))
+  (interactive)
+  (if-let ((symbol (thing-at-point 'symbol)))
+      (let ((regexp (format "\\_<%s\\_>" (regexp-quote symbol))))
+        (when (looking-back regexp (- (point) (length symbol)))
+          (forward-symbol -1))
+        (unless (re-search-backward regexp nil t)
+          (user-error "Symbol `%s' not found" symbol)))
+    (user-error "No symbol at point")))
 
 (defun embark-compose-mail (address)
   "Compose email to ADDRESS."