[Fix] Fix Segformer checkpoint URLs

[AkideLiu]

Thanks for your contribution and we appreciate it a lot. The following instructions would make your pull request more healthy and more easily get feedback. If you do not understand some items, don't worry, just make the pull request and seek help from maintainers.

Motivation

Segformer checkpoint URLs.

Original URL:

curl -I https://download.openmmlab.com/mmsegmentation/v0.5/pretrain/segformer/mit_b5_20220624-658746d9.pthh
HTTP/1.1 404 Not Found
Server: AliyunOSS
Date: Sat, 16 Jul 2022 06:16:59 GMT
Content-Type: application/xml
Content-Length: 310
Connection: keep-alive
x-oss-request-id: 62D257DB33FDC32BE06E6587
x-oss-server-time: 2

It should be

curl -I https://download.openmmlab.com/mmsegmentation/v0.5/pretrain/segformer/mit_b5_20220624-658746d9.pth
HTTP/1.1 200 OK
Server: AliyunOSS
Date: Sat, 16 Jul 2022 06:17:02 GMT
Content-Type: application/octet-stream
Content-Length: 326083151
Connection: keep-alive
x-oss-request-id: 62D257DEF8BE36581C235769
Accept-Ranges: bytes
ETag: "D6F74C9A629FF8069A400BA006DE5D71"
Last-Modified: Fri, 24 Jun 2022 08:34:51 GMT
x-oss-object-type: Normal
x-oss-hash-crc64ecma: 13752895834074269699
x-oss-storage-class: Standard
x-oss-version-id: CAEQQxiBgMDegrPTjBgiIDdjMzlkZDg2OGJjYzRkODVhMTQyYmQ3NDFjMzFhMGE2
Content-MD5: 1vdMmmKf+AaaQAugBt5dcQ==
x-oss-server-time: 92

Modification

Modify the URL of checkout files

BC-breaking (Optional)

No

Use cases (Optional)

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDet or MMDet3D.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[codecov]

Codecov Report

Merging #1785 (7ea4494) into master (0e37281) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1785   +/-   ##
=======================================
  Coverage   89.04%   89.04%           
=======================================
  Files         144      144           
  Lines        8636     8636           
  Branches     1458     1458           
=======================================
  Hits         7690     7690           
  Misses        706      706           
  Partials      240      240           

Flag	Coverage Δ
unittests	89.04% <ø> (ø)

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[xiexinch]

Hi @AkideLiu,
Hi, very thankful for your nice PR. We'll merge it asap. :)

[jason102811]

akideliu，您好！您在MMSeg项目中给我们提的PR非常重要，感谢您付出私人时间帮助改进开源项目，相信很多开发者会从你的PR中受益。
我们非常期待与您继续合作，OpenMMLab专门成立了贡献者组织MMSIG，为贡献者们提供开源证书、荣誉体系和专享好礼，可通过添加微信：openmmlabwx 联系我们（请备注mmsig+GitHub id），由衷希望您能加入！
Dear akideliu,
First of all, we want to express our gratitude for your significant PR in the MMSeg project. Your contribution is highly appreciated, and we are grateful for your efforts in helping improve this open-source project during your personal time. We believe that many developers will benefit from your PR.
We are looking forward to continuing our collaboration with you. OpenMMLab has established a special contributors' organization called MMSIG, which provides contributors with open-source certificates, a recognition system, and exclusive rewards. You can contact us by adding our WeChat（if you have WeChat): openmmlabwx, or join in our discord： https://discord.gg/qH9fysxPDW. We sincerely hope you will join us!
Best regards！ @AkideLiu