SPFx project upgrade from 1.7.1 to 1.8.2 suggests both rush 2.7 and 2.9 install

Upgrading a project from 1.7.1 to 1.8.2, the install commands suggest both `@microsoft/rush-stack-compiler-2.7` and `@microsoft/rush-stack-compiler-2.9`

```
npm i @microsoft/sp-build-web@1.8.2 @microsoft/sp-module-interfaces@1.8.2 @microsoft/sp-webpart-workbench@1.8.2 @microsoft/sp-tslint-rules@1.8.2 @microsoft/rush-stack-compiler-2.9@0.7.7 @microsoft/rush-stack-compiler-2.7@0.4.0 -DE
```