examples/retry: remove waitForReady from service config

[dfawley]

This setting is irrelevant, so remove it to avoid any confusion.

Fixes #7440

RELEASE NOTES: none

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.30%. Comparing base (0231b0d) to head (e164dd5).
Report is 11 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7450      +/-   ##
==========================================
- Coverage   81.44%   81.30%   -0.14%     
==========================================
  Files         352      354       +2     
  Lines       26919    27076     +157     
==========================================
+ Hits        21924    22014      +90     
- Misses       3804     3844      +40     
- Partials     1191     1218      +27     

Files	Coverage Δ
rpc_util.go	81.63% <ø> (ø)

... and 35 files with indirect coverage changes

[purnesh42H]

We should update in these two places as well

• https://github.com/grpc/grpc-go/blob/master/test/retry_test.go

• grpc-go/examples/features/retry/README.md

  Line 44 in 3eb0145

  "waitForReady": true,

Also, might be good to put a note in documentation that this setting is not relevant for retry policies

[dfawley]

IIRC, in the tests, WFR is used as a trick to detect that the service config was properly applied by the client. I'll update the corresponding doc for the example and look at the WFR docstring.

[dfawley]

PTAL

[purnesh42H]

lgtm