a possible easy way (but be careful) .....
Select one object with the effect applied.
Highlight the effect in the Appearance Panel.
From the menu, choose
Select > Same > Appearance Attribute
From the Appearance Panel menu, choose
Reduce to Basic Appearance
This will, in effect, remove everything other than the fill and stroke for the selected objects. So, if you have custom opacity settings or other effects on the objects, it will remove those as well. This is why I posted be careful. This is not always an ideal solution and it greatly depends on what the overall appearance options are for each individual object.
Unfortunately, once you get these objects selected this way, there's no function or feature to just remove the common effect easily. (Why, I don't know)
A global workflow which may prove easier in the future....
This somewhat depends on the file structure. Let's hope you've utilized Layers well. If not, you may need to restructure layers accordingly. Artboards won't be effected by this at all. There's no way to apply appearance settings to a specific artboard (which there were).
If you have a file with many layers:
Note, each rectangle is on its own layer.
You can then highlight all the layers in the Layer Panel and choose Collect in New Layer from the Layer Panel menu:
This create one master layer with all your existing layers as sub-layers.
You can then click the target on the right of the new master layer (the little circle) which will select the Layer itself.
Note the change in the Appearance panel. It indicates a Layer is selected.
Now, add your raster effect. It will be applied to all contents of the master layer. Note the grey filled circle to the right of the layer name in the Layer Panel now (often referred to as a "meatball"). This indicates an appearance has been applied to the layer itself.
If you need to alter individual objects, you still can by selecting them and editing.
If you need to remove the raster effect, simply click the master layer target again, you'll see the raster effect in the Appearance Panel, and just delete the effect from the layer's appearance.