[FLINK-20905][k8s] Format the description of 'kubernetes.container.image' option

[yuruguo]

What is the purpose of the change

The description of ConfigOption 'kubernetes.container.image' has a URL link, so a reasonable way is to use Text Description with Link to format.

Brief change log

• The ConfigOption 'kubernetes.container.image' use text with link to descript

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes / no)
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): (yes / no / don't know)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: (yes / no / don't know)
• The S3 file system connector: (yes / no / don't know)

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

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Last check on commit 9e0cb70 (Fri May 28 07:06:12 UTC 2021)

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[wangyang0918]

Thanks for creating this PR. This change makes sense. I left a minor comments. Could you please get it integrated before merging.

[wangyang0918]

Suggested change

	"DockerHub"))
	"apache/flink DockerHub repository"))

[wangyang0918]

Maybe using "apache/flink DockerHub repository" is better since the official docker images are also located in the DockerHub.

[yuruguo]

Thanks for you suggestion @wangyang0918, I have updated and submitted again, please take a look.

[wangyang0918]

LGTM. +1 for merging.

[wangyang0918]

Suggested change

	"https://hub.docker.com/r/apache/flink",
	"https://hub.docker.com/r/apache/flink?tab=tags",

nit: Maybe also add the "?tab=tags" is better to align with official image link.

[yuruguo]

Ok, but I tried it and found that https://hub.docker.com/r/apache/flink?tab=tags is not align with the https://hub.docker.com/_/flink?tab=tags, maybe the correct link should be https://hub.docker.com/r/apache/flink/tags

[wangyang0918]

Strange. But you are right. Could you update it?

[yuruguo]

Done. Take a look, THX!

[wangyang0918]

cc @xintongsong Could you have a final check and help with merging?

[xintongsong]

TBH, I think the current description for this configuration option is a bit confusing for the users. It recommends two images, without explaining the differences between them and how should users choose between them.

However, the purpose of this PR is simply to improve the format for the links. To this purpose, the changes look good to me. Merging this once passing the ci tests.