docs(angular.copy): Fixed getter/setter formatting

[thatshubham]

This is tiny documentation fix. Fixed the formatting to getter/setter

AngularJS is in LTS mode

We are no longer accepting changes that are not critical bug fixes into this project.
See https://blog.angular.io/stable-angularjs-and-long-term-support-7e077635ee9c for more detail.

Does this PR fix a regression since 1.7.0, a security flaw, or a problem caused by a new browser version?

What is the current behavior? (You can also link to an open issue here)

What is the new behavior (if this is a feature change)?

Does this PR introduce a breaking change?

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Fix/Feature: Docs have been added/updated
• Fix/Feature: Tests have been added; existing tests pass

Other information:

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[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

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[thatshubham]

@googlebot I signed it!

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CLAs look good, thanks!

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CLAs look good, thanks!

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[gkalpak]

LGTM 👍 Thx, @thatshubham!
(I will update the commit messages to adhere to our conventions and merge.)