Desktop: Fix viewer and panel plugins that check for the presence of exports fail to load

[personalizedrefrigerator]

Summary

This reverts commit c197a83. See this issue report on the forum.

The Function Plot plugin (and possibly other plugins) check whether a variable called exports exists to determine whether running in a NodeJS or browser environment, then export content accordingly.

c197a83 had the effect of fixing a nonfatal error in plugins that use the default plugin template. An alternate approach could be to modify the default plugin template to target web instead of node for panel/dialog/viewer scripts. See the forum post for more details.

Testing plan

1. Install "Function Plot" plugin.
2. Create a new note with the function plot example note content.
3. Verify that plotted functions render in the viewer.