docs(readme): change Kafka to Apache Kafka

[Sunt-ing]

What's changed and what's your intention?

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Please explain IN DETAIL what the changes are in this PR and why they are needed:

• Summarize your change (mandatory)
• How does this PR work? Need a brief introduction for the changed logic (optional)
• Describe clearly one logical change and avoid lazy messages (optional)
• Describe any limitations of the current code (optional)

Change Kafka to Apache Kafka.

Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests

Refer to a related PR or issue link (optional)

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[StrikeW]

LGTM

[codecov]

Codecov Report

Merging #1725 (90a69cc) into main (8c8401b) will decrease coverage by 19.21%.
The diff coverage is 5.28%.

❗ Current head 90a69cc differs from pull request most recent head 1e2f301. Consider uploading reports for the commit 1e2f301 to get more accurate results

@@             Coverage Diff             @@
##             main    #1725       +/-   ##
===========================================
- Coverage   71.31%   52.09%   -19.22%     
===========================================
  Files         599      621       +22     
  Lines       77662   108564    +30902     
===========================================
+ Hits        55384    56558     +1174     
- Misses      22278    52006    +29728     

Flag	Coverage Δ
rust	52.09% <5.28%> (-19.22%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
rust/prost/src/common.serde.rs	0.00% <0.00%> (ø)
rust/prost/src/ddl_service.rs	0.00% <0.00%> (ø)
rust/prost/src/ddl_service.serde.rs	0.00% <0.00%> (ø)
rust/prost/src/hummock.serde.rs	0.00% <ø> (ø)
rust/prost/src/meta.serde.rs	0.00% <ø> (ø)
rust/prost/src/plan.serde.rs	2.37% <ø> (ø)
rust/prost/src/stream_plan.serde.rs	11.15% <ø> (ø)
rust/prost/src/stream_service.serde.rs	0.00% <0.00%> (ø)
rust/prost/src/task_service.serde.rs	0.00% <0.00%> (ø)
rust/prost/src/meta.rs	0.73% <0.82%> (ø)
... and 17 more

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[TennyZhuang]

LGTM