add header providers to PublisherStubSettings

[vinnyspb]

HeaderProvider is missing from PublisherStubSettings initialisation

[google-cla]

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[google-cla]

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).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed (or fixed any issues), please reply here with @googlebot I signed it! and we'll verify it.

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What to do if you already signed the CLA

Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
• The email used to register you as an authorized contributor must also be attached to your GitHub account.

ℹ️ Googlers: Go here for more info.

[codecov]

Codecov Report

Merging #294 into master will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #294      +/-   ##
============================================
+ Coverage     79.18%   79.23%   +0.04%     
  Complexity      317      317              
============================================
  Files            21       21              
  Lines          2888     2889       +1     
  Branches        155      155              
============================================
+ Hits           2287     2289       +2     
  Misses          537      537              
+ Partials         64       63       -1     

Impacted Files	Coverage Δ	Complexity Δ
...ain/java/com/google/cloud/pubsub/v1/Publisher.java	88.00% <100.00%> (+0.03%)	46.00 <0.00> (ø)
.../com/google/cloud/pubsub/v1/MessageDispatcher.java	85.36% <0.00%> (+0.48%)	26.00% <0.00%> (ø%)

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[davidxia]

Nice catch! I think you'll need to sign the contribute license agreement (CLA).