fix typos

Author: hellock

docs/CHANGELOG.md

@@ -8,9 +8,9 @@ This release mainly improves the code quality and add more docstrings.
 - Documentation is online now: https://mmdetection.readthedocs.io.
 - Support new models: [ATSS](https://arxiv.org/abs/1912.02424).
 - DCN is now available with the api `build_conv_layer` and `ConvModule` like the normal conv layer.
-- A tool to collect environment infomation is available for trouble shoting.
+- A tool to collect environment information is available for trouble shooting.
 
-**Bug Fixes**
+**Bug Fixes**  (use "git pull" to update your local branch)
 - Fix the incompatibility of the latest numpy and pycocotools. (#2024)
 - Fix the case when distributed package is unavailable, e.g., on Windows. (#1985)
 - Fix the dimension issue for `refine_bboxes()`. (#1962)
@@ -22,7 +22,7 @@ This release mainly improves the code quality and add more docstrings.
 
 **Improvements**
 - Enhance AssignResult and SamplingResult. (#1995)
-- Add ability to overwite existing module in Registry. (#1982)
+- Add ability to overwrite existing module in Registry. (#1982)
 - Reorganize requirements and make albumentations and imagecorruptions optional. (#1969)
 - Check NaN in `SSDHead`. (#1935)
 - Encapsulate the DCN in ResNe(X)t into a ConvModule & Conv_layers. (#1894)