Fix vpRealSense2::getProductLine()

[s-trinh]

Following error occurs when running example/device/framegrabber/grabRealSense2.cpp code with the D455 sensor:

• Frame didn't arrive within 15000

Tested with:

• ./grabRealSense2
• ./testRealSense2_D435
• ./testRealSense2_D435_opencv

More info:

• Intel RealSense D455
• Firmware Version: 5.12.7.100
• Use Realsense2: yes (ver 2.54.2)

The error Frame didn't arrive within 15000 still happens sometimes and relaunching the executable or unplug/plug the device seems to "solve" the issue.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.63%. Comparing base (1675840) to head (ba59390).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1371      +/-   ##
==========================================
- Coverage   45.63%   45.63%   -0.01%     
==========================================
  Files        1069     1069              
  Lines      108080   108080              
  Branches    18710    18708       -2     
==========================================
- Hits        49325    49324       -1     
- Misses      58755    58756       +1     

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[fspindle]

@s-trinh Thanks again ;-)