[docs] Fix manifest URL for GKE + Azure

[schallert]

What this PR does / why we need it: This PR fixes broken links for the cloud-generic.yaml manifests in the GKE and Azure sections of the deployment guide.

Which issue this PR fixes: None.

Special notes for your reviewer: None.

[aledbf]

/approve
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf, schallert

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[aledbf]

@schallert thanks!

[codecov-io]

Codecov Report

Merging #2544 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #2544   +/-   ##
======================================
  Coverage    40.7%   40.7%           
======================================
  Files          73      73           
  Lines        5034    5034           
======================================
  Hits         2049    2049           
  Misses       2711    2711           
  Partials      274     274

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