[SPARK-25382][SQL][PYSPARK] Remove ImageSchema.readImages in 3.0

[WeichenXu123]

What changes were proposed in this pull request?

This PR proposes to remove the deprecate ImageSchema.readImages.

How was this patch tested?

UT.

[SparkQA]

Test build #108099 has finished for PR 25245 at commit b21aa23.

• This patch fails Python style tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
• raise RuntimeError(\"Creating instance of _ImageUtils class is disallowed.\")

[srowen]

I'll tag the JIRA with release-notes and add a description of the breaking change. Looks OK in principle.

[SparkQA]

Test build #108103 has finished for PR 25245 at commit 450b9d8.

• This patch fails Python style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[WeichenXu123]

Comment.

[SparkQA]

Test build #108104 has finished for PR 25245 at commit 086e0ae.

• This patch fails MiMa tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #108117 has finished for PR 25245 at commit bcb4490.

• This patch fails PySpark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[WeichenXu123]

Comment.

[SparkQA]

Test build #108144 has finished for PR 25245 at commit 6bbb35b.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[srowen]

WDYT @WeichenXu123 ? I'm OK with removing less in this change if there's any question about what to keep.

[WeichenXu123]

I am ok with @HyukjinKwon 's opinion. Will update PR then.

[HyukjinKwon]

Thanks @srowen and @WeichenXu123

[SparkQA]

Test build #108384 has finished for PR 25245 at commit 8fb3f87.

• This patch fails MiMa tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
• class _ImageSchema(object):
• raise RuntimeError(\"Creating instance of _ImageSchema class is disallowed.\")

[SparkQA]

Test build #108389 has finished for PR 25245 at commit 02b4853.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #108388 has finished for PR 25245 at commit cebc9d0.

• This patch passes all tests.
• This patch does not merge cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #108434 has finished for PR 25245 at commit 6460c7a.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[HyukjinKwon]

Merged to master.