Fix PnP init regression from e14cb87 (#3389)

This regressed with  e14cb87 / #3385, which went live on Monday (2 days ago).

1. The base `PlanningSheet` class initializing `goalStart`
2. `goalColumn` was read, which read the `revisionCell`
3. `revisionCell` wasn't initialized yet, because it is defined in child classes.

Switching `goalStart` to be lazy fixes this.
It was also the only property in the base class that was eagerly initialized.

Author: CarsonF

src/components/pnp/planning-sheet.ts

@@ -65,10 +65,12 @@ export abstract class PlanningSheet extends Sheet {
     return this.column('Q');
   }
 
-  get goals(): Range<PlanningSheet> {
+  @Once() get goals(): Range<PlanningSheet> {
     return this.range(this.goalsStart, this.goalsEnd);
   }
-  protected goalsStart = this.cell(this.goalColumn, 23);
+  @Once() protected get goalsStart() {
+    return this.cell(this.goalColumn, 23);
+  }
   @Once() protected get goalsEnd() {
     return this.sheetRange.end.row.cell(this.goalColumn);
   }