Update hintColor value for Material

[JuYeong0413]

Description

Updated hintColor value for Material.

Both Dark mode documentation and Light mode documentation states that

Medium-emphasis text and hint text have opacities of 60%

This pull request updates hintColor value in dark mode to Colors.white60(corresponds to 60% opacity).
For light mode, updates value to Colors.black.withOpacity(0.6) since there's no constant for black60.

For golden file changes:

input_decorator.outline_icon_label.ltr.png

input_decorator.outline_icon_label.rtl.png

Related Issues

Fixes #55329

Tests

None. Only color values changed.
If I need to add a test for this, please let me know. :)

Checklist

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• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I signed the CLA.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I updated/added relevant documentation (doc comments with ///).
• All existing and new tests are passing.
• The analyzer (flutter analyze --flutter-repo) does not report any problems on my PR.
• I am willing to follow-up on review comments in a timely manner.

Breaking Change

Did any tests fail when you ran them? Please read Handling breaking changes.

• No, no existing tests failed, so this is not a breaking change.
• Yes, this is a breaking change.

[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat.

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

[skia-gold]

Gold has detected about 6 untriaged digest(s) on patchset 1.
View them at https://flutter-gold.skia.org/cl/github/65036

[flutter-dashboard]

Golden file changes have been found for this pull request. Click here to view and triage (e.g. because this is an intentional change).

If you are still iterating on this change and are not ready to resolve the images on the Flutter Gold dashboard, consider marking this PR as a draft pull request above. You will still be able to view image results on the dashboard, commenting will be silenced, and the check will not try to resolve itself until marked ready for review.

For more guidance, visit Writing a golden file test for package:flutter.

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

Changes reported for pull request #65036 at sha 35f95e0

[JuYeong0413]

Hi @Piinks, this is my first time making golden file changes, so I might have not fully understood about Golden File Test.
(Sorry for pinging, looks like you're busy these days!)

I ran flutter test locally with --update-goldens flag and got updated images.
From the wiki, it seems like I should add goldens in my PR description, but I didn't get it. Does this mean that I should I open a pull request in flutter/goldens repository?
The README in the goldens repository says:

The flutter/goldens repository has been deprecated from its use for the flutter/flutter repository’s golden file testing.

so I'm a bit confused about what should I do next with updated images...

[Piinks]

Hey @JuYeong0413! You can just include the image in your PR description above. :)
The flutter-dashboard comment above provided a link to the dashboard where you can see the images that were generated by the tests run here. If they look as you expect we can approve them and they'll be checked in on the dashboard.
Let me know if the images on the dashboard look right, here is the link again:

Click here to view and triage

[JuYeong0413]

Ah, now I've got it. Thanks a lot @Piinks!
I've added images in the description. Please take a look when you have time. :)

[Piinks]

Validated this change is covered by golden file tests.
Thank you fort he contribution @JuYeong0413 ! LGTM!