[imaging browser] Remove apparently unused button

[maximemulder]

Brief summary of changes

While browsing Loris code, I stumbled upon a button in view session that appears to be broken / dead code in the imaging browser:

• The button points to the BrainBrowser/display.html URL. However, there seems is no such file in LORIS.
• The button uses a relative link, which is probably wrong.
• The button is only displayed if a session has a corresponding "obj" file in the database. However, there is no such file in Rainsinbread.

Thus, I open this PR to remove this button. But before merging it, I'd like to know if anyone has any information regarding the button or its display condition.

Pinging the imaging squad @ridz1208 @cmadjar @laemtl.

[maximemulder]

I probably should have looked at that earlier, but considering this button seems to have been untouched for more than 10 years, I'd say there is a 100% chance it needs to be removed. I am still curious about the "obj" files though, I don't know what those are.

[cmadjar]

I am not sure that this button should be removed. "obj" files are specific derivatives image files (which raisin bread don't have). I don't know if some projects are still using it. I think this should be brought up at the next LORIS call to see if any project uses that feature.
@maximemulder can you add this to the next LORIS call agenda?

[maximemulder]

Okay, added!

[maximemulder]

We discussed this subject in the latest LORIS meeting, and concluded no one depends on this button. The page display.html probably existed at some point, but it was removed a long time ago (before version 15). So we are in favor of removing this button @cmadjar (unless you have some more questions).

[cmadjar]

Sounds good! @driusan ready for you :-)