Removes ignored const from return type

[Jdavid1001-zz]

See #2425

[grpc-kokoro]

Thanks for your pull request. The automated tests will run as soon as one of the admins verifies this change is ok for us to run on our infrastructure.

[grpc-kokoro]

Thanks for your pull request. The automated tests will run as soon as one of the admins verifies this change is ok for us to run on our infrastructure.

[bazel-io]

Can one of the admins verify this patch?

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

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[xfxyjwf]

ok to test

[xfxyjwf]

@Jdavid1001 The CLA bot complaints about you not signing google CLA. I guess you haven't added your account to google organization?

[Jdavid1001-zz]

@xfxyjwf I've joined Google now. Does that make it fine?

[xfxyjwf]

Can you reply as instructed by the google bot?

Once you've signed, please reply here (e.g. I signed it!) and we'll verify. Thanks.

[Jdavid1001-zz]

I signed it!

[xfxyjwf]

@Jdavid1001 The signcla checker still reports you haven't signed Google CLA.

[googlebot]

CLAs look good, thanks!

[Jdavid1001-zz]

Had to recommit with my @google.com email. Please let me know if there are any other concerns.

[xfxyjwf]

Thanks!