FIX: Ranges selected should be absolute.

Sheet1!$D$1 rather than Sheet1!D1

There reason is that if we extend a formula that has those will behave in
surprising ways.

webapp/src/components/tests/util.test.ts

@@ -41,5 +41,5 @@ test("format range to get the full formula", async () => {
   };
   const worksheetNames = ["Sheet1", "Notes"];
 
-  expect(getFullRangeToString(selectedView, worksheetNames)).toBe("Sheet1!H1");
+  expect(getFullRangeToString(selectedView, worksheetNames)).toBe("Sheet1!$H$1");
 });