fixes for getting the samples to work

[vinayada1]

Description

1. grpc sample needs a small fix.
2. runtime behavior defaults the data content type to text. Needs to be explicitly set by the sdk

Issue reference

We strive to have all PR being opened based on an issue, where the problem or feature have been discussed prior to implementation.

Please reference the issue this PR will close: #[issue number]

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation

[codecov]

Codecov Report

Merging #570 (4d55e38) into release-1.0.0 (aa41915) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@              Coverage Diff               @@
##           release-1.0.0     #570   +/-   ##
==============================================
  Coverage          65.84%   65.85%           
==============================================
  Files                120      120           
  Lines               3956     3957    +1     
  Branches             436      436           
==============================================
+ Hits                2605     2606    +1     
  Misses              1231     1231           
  Partials             120      120           

Impacted Files	Coverage Δ
src/Dapr.Client/DaprClientGrpc.cs	87.68% <100.00%> (+0.02%)	⬆️

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