ign -> gz : Remove redundant namespace references

[methylDragon]

Part of: gazebo-tooling/release-tools#784

[codecov]

Codecov Report

Merging #345 (6cdd382) into ign-transport8 (9ba73b7) will decrease coverage by 0.01%.
The diff coverage is 84.61%.

❗ Current head 6cdd382 differs from pull request most recent head 2b71fdf. Consider uploading reports for the commit 2b71fdf to get more accurate results

@@                Coverage Diff                 @@
##           ign-transport8     #345      +/-   ##
==================================================
- Coverage           83.63%   83.61%   -0.02%     
==================================================
  Files                  51       51              
  Lines                5035     5035              
==================================================
- Hits                 4211     4210       -1     
- Misses                824      825       +1     

Impacted Files	Coverage Δ
src/Packet.cc	0.00% <0.00%> (ø)
src/ign.cc	99.14% <83.33%> (ø)
log/src/Playback.cc	93.51% <100.00%> (ø)
log/src/Recorder.cc	87.20% <100.00%> (ø)
log/src/cmd/LogCommandAPI.cc	62.50% <100.00%> (ø)
src/NodeShared.cc	78.95% <100.00%> (ø)
include/ignition/transport/Discovery.hh	85.86% <0.00%> (-0.21%)	⬇️

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[caguero]

Looks good!