Revert "PY-83323 Jupyter: Create JupyterKernelTaskExecutor and refactor there all standard methods for JupyterTaskExecutor"

This reverts commit 2a01013cd6e41e62855dc9ebd65afe412545da37.

GitOrigin-RevId: 0fc9735099765072d5f69a076820351d96623fe1

Author: kirilenko-jb

notebooks/visualization/src/com/intellij/notebooks/visualization/NotebookCellLinesUtils.kt

@@ -0,0 +1,7 @@
+package com.intellij.notebooks.visualization
+
+import com.intellij.openapi.editor.Document
+
+fun Document.getContentText(cell: NotebookCellLines.Interval): CharSequence {
+  return cell.getContentText(this)
+}