[Error] Remove deprecations in ti.ui in 1.6.0 (#7229)

Issue: #7189 

### Brief Summary

python/taichi/ui/ui.py

@@ -20,8 +20,8 @@ def make_camera():
         >>> camera = ti.ui.make_camera()
     """
     warnings.warn(
-        "`ti.ui.make_camera()` is deprecated, please use `ti.ui.Camera()` instead",
-        DeprecationWarning)
+        "`ti.ui.make_camera()` is deprecated, and will be removed in Taichi v1.6.0. "
+        "Please use `ti.ui.Camera()` instead", DeprecationWarning)
     return Camera()
 
 

python/taichi/ui/window.py

@@ -151,8 +151,8 @@ def write_image(self, filename):
             filename (str): output filename.
         """
         warnings.warn(
-            "`Window.write_image()` is renamed to `Window.save_image()`",
-            DeprecationWarning)
+            "`Window.write_image()` is deprecated, and it will be removed in Taichi v1.6.0. "
+            "Please use `Window.save_image()` instead.", DeprecationWarning)
         return self.save_image(filename)
 
     def save_image(self, filename):

tests/python/test_deprecation.py

@@ -2,6 +2,7 @@
 import tempfile
 
 import pytest
+from taichi._lib import core as _ti_core
 
 import taichi as ti
 from tests import test_utils
@@ -197,6 +198,29 @@ def ker(tex: ti.types.rw_texture(num_dimensions=2, lod=0)):
                 tex.store(ti.Vector([i, j]), ti.Vector([ret, 0.0, 0.0, 0.0]))
 
 
+@pytest.mark.skipif(not _ti_core.GGUI_AVAILABLE, reason="GGUI Not Available")
+@test_utils.test(arch=ti.cpu)
+def test_deprecate_ti_ui_window():
+    window = ti.ui.Window("Diff SPH", (256, 256), show_window=False)
+    with pytest.warns(
+            DeprecationWarning,
+            match=
+            r"`Window\.write_image\(\)` is deprecated, and it will be removed in Taichi v1\.6\.0\. "
+    ):
+        window.write_image("deprecate.png")
+
+
+@pytest.mark.skipif(not _ti_core.GGUI_AVAILABLE, reason="GGUI Not Available")
+@test_utils.test(arch=ti.cpu)
+def test_deprecate_ti_ui_make_camera():
+    with pytest.warns(
+            DeprecationWarning,
+            match=
+            r"`ti\.ui\.make_camera\(\)` is deprecated, and will be removed in Taichi v1\.6\.0\. "
+    ):
+        ti.ui.make_camera()
+
+
 @test_utils.test()
 def test_deprecation_in_taichi_init_py():
     with pytest.warns(