fix(timestamp): remove old SCHEDULED/DEADLINE timestamp

When using `date-picker` to update the SCHEDULED/DEADLINE timestamp by
clicking an existing one, logseq will add a new timestamp instead of
updating the old one. This patch fixs this issue.

src/main/frontend/handler/editor.cljs

@@ -1006,7 +1006,8 @@
     (when-let [block (db/pull [:block/uuid block-id])]
       (let [{:block/keys [content scheduled deadline format]} block
             content (or (state/get-edit-content) content)
-            new-content (text/add-timestamp content key value)]
+            new-content (-> (text/remove-timestamp content key)
+                            (text/add-timestamp key value))]
         (when (not= content new-content)
           (if-let [input-id (state/get-edit-input-id)]
             (state/set-edit-content! input-id new-content)

src/main/frontend/text.cljs

@@ -240,3 +240,13 @@
                            new-line
                            (rest new-lines))))]
     (string/join "\n" new-lines)))
+
+(defn remove-timestamp
+  [content key]
+  (let [lines (string/split-lines content)
+        new-lines (filter (fn [line]
+                            (not (string/starts-with? (string/lower-case line) key)))
+                          lines)]
+    (println "new-lines" new-lines)
+    (string/join "\n" new-lines)))
+