Use GzSpinBox instead of IgnSpinBox in ViewAngle plugin

[caguero]

🦟 Bug fix

Summary

I'm getting this error in a downstream project (VRX) while trying to load the ViewAngle GUI plugin:

[GUI] [Err] [Plugin.cc:147] Failed to instantiate QML file [:/ViewAngle/ViewAngle.qml].
[ruby $(which gz) sim-1] * file::/ViewAngle/ViewAngle.qml:350:5: IgnSpinBox is not a type

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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[codecov]

Codecov Report

Merging #1969 (1d073e9) into gz-sim7 (f06d37a) will increase coverage by 0.02%.
The diff coverage is 73.52%.

❗ Current head 1d073e9 differs from pull request most recent head 675434e. Consider uploading reports for the commit 675434e to get more accurate results

@@             Coverage Diff             @@
##           gz-sim7    #1969      +/-   ##
===========================================
+ Coverage    65.04%   65.06%   +0.02%     
===========================================
  Files          352      352              
  Lines        28292    28318      +26     
===========================================
+ Hits         18402    18426      +24     
- Misses        9890     9892       +2     

Impacted Files	Coverage Δ
...rc/systems/ackermann_steering/AckermannSteering.hh	100.00% <ø> (ø)
...rc/systems/ackermann_steering/AckermannSteering.cc	80.09% <73.52%> (-0.45%)	⬇️

... and 2 files with indirect coverage changes

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