Review and possibly remove additional morphic patches in JfP

[ericwinger]

There were a number of morphic walkbacks that had to be worked around in JfP when development was being done in Pharo 11. Now that JfP is only available with Pharo 12, it was suggested to remove these patches.

The suggested patches are here #149 (comment) (see below)

Need to review and test without these patches.

"Thanks! There are a few similar patches to other methods that should perhaps be removed as well: #recomputeSelection on RubAbstractTextArea, #drawOn: on RubLineNumberDisplayer, #drawOn: on RubOpeningClosingDelimiterDecorator, #whenExtentChanged: on RubTextSegmentMorph, and #computeVertices on RubUnderlinedSegmentMorph (which conflicts with the changes of Pharo commit 1046ab4f05)."

[ericwinger]

I pulled the overrides and ran the tests which passed. We'll need to keep an eye out for red X boxes of death and restore overrides if necessary.