Fix dangling "see ..." and clean up complex class template specializations

[Rageking8]

Fix dangling "see ..." by using the one in complex<long double>:

cpp-docs/docs/standard-library/complex-long-double.md

Line 49 in 087e22d

For more information on the class template `complex` and its members, see [complex Class](../standard-library/complex-class.md).

[prmerger-automator]

@Rageking8 : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change.

[learn-build-service-prod]

Learn Build status updates of commit 30ab0f9:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/standard-library/complex-double.md	✅Succeeded
docs/standard-library/complex-float.md	✅Succeeded
docs/standard-library/complex-long-double.md	✅Succeeded

For more details, please refer to the build report.

[v-dirichards]

@TylerMSFT

Can you review the proposed changes?

Important: When the changes are ready for publication, adding a #sign-off comment is the best way to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged"
@MicrosoftDocs/public-repo-pr-review-team

[v-dirichards]

@TylerMSFT Could you review this proposed update to your article and enter #sign-off in a comment if it's ready to merge?

Thanks!

[TylerMSFT]

I see that you saw to remove the unnecessary see's. Thank you :-)

[TylerMSFT]

#sign-off