fix(docs): rename task-handler.md to timer-handler.md (#3203)

since all task facility is already switched to timer facility

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

docs/porting/index.md

@@ -14,7 +14,7 @@
    display
    indev
    tick
-   task-handler
+   timer-handler
    sleep
    os
    log

docs/porting/project.md

@@ -67,4 +67,4 @@ To use the graphics library you have to initialize it and setup required compone
 2. Initialize your drivers.
 3. Register the display and input devices drivers in LVGL.  Learn more about [Display](/porting/display) and [Input device](/porting/indev) registration.
 4. Call `lv_tick_inc(x)` every `x` milliseconds in an interrupt to report the elapsed time to LVGL. [Learn more](/porting/tick).
-5. Call `lv_timer_handler()` every few milliseconds to handle LVGL related tasks. [Learn more](/porting/task-handler).
+5. Call `lv_timer_handler()` every few milliseconds to handle LVGL related tasks. [Learn more](/porting/timer-handler).

docs/porting/timer-handler.md

@@ -1,8 +1,8 @@
 ```eval_rst
 .. include:: /header.rst
-:github_url: |github_link_base|/porting/task-handler.md
+:github_url: |github_link_base|/porting/timer-handler.md
 ```
-# Task Handler
+# Timer Handler
 
 To handle the tasks of LVGL you need to call `lv_timer_handler()` periodically in one of the following:
 - *while(1)* of *main()* function