Fix/traversability ghost obstacles

[VAM7686]

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Description

Fixes ghost obstacles in traversability layer by applying morphological transforms.

This PR does the following:

• Fixes ghost obstacles in traversability layer

Fixes #836

Testing steps (If relevant)

Test Case 1

1. Run roslaunch igvc_gazebo ramp_lane.launch
2. Run roslaunch igvc_navigation navigation_simulation.launch

Expectation: Robot able to navigate over ramp smoothly without any ghost obstacles.

Self Checklist

• [x] I have formatted my code using make format
• [x] I have tested that the new behaviour works