Update swagger-codegen-cli URL

[jinchihe]

fixes: #1166

[root@jinchi1 ~]# wget http://central.maven.org/maven2/io/swagger/swagger-codegen-cli/2.4.6/swagger-codegen-cli-2.4.6.jar
--2020-06-14 19:39:27--  http://central.maven.org/maven2/io/swagger/swagger-codegen-cli/2.4.6/swagger-codegen-cli-2.4.6.jar
Resolving central.maven.org (central.maven.org)... failed: Name or service not known.
wget: unable to resolve host address 'central.maven.org'

[root@jinchi1 ~]# wget http://search.maven.org/maven2/io/swagger/swagger-codegen-cli/2.4.6/swagger-codegen-cli-2.4.6.jar
--2020-06-14 20:03:53--  http://search.maven.org/maven2/io/swagger/swagger-codegen-cli/2.4.6/swagger-codegen-cli-2.4.6.jar
Resolving search.maven.org (search.maven.org)... 18.234.11.249, 3.227.158.232
Connecting to search.maven.org (search.maven.org)|18.234.11.249|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 14670887 (14M) [application/java-archive]
Saving to: 'swagger-codegen-cli-2.4.6.jar.1'

100%[=====================================================================================================>] 14,670,887  3.28MB/s   in 9.1s

2020-06-14 20:04:03 (1.53 MB/s) - 'swagger-codegen-cli-2.4.6.jar.1' saved [14670887/14670887]

[kubeflow-bot]

This change is 

[coveralls]

Coverage remained the same at 96.667% when pulling fd7a3f6 on jinchihe:update_swagger-codegen-cli_url into 2479837 on kubeflow:master.

[gaocegege]

/lgtm
/approve

[k8s-ci-robot]

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[jinchihe]

@gaocegege Thanks Ce!