[bug] Matrix display names are not being overwritten when using replace argument

See for example this config: https://github.com/Azure/azure-sdk-for-net/blob/main/eng/pipelines/templates/stages/platform-matrix.json#L2-L5

And the display output is the variable value, not the display name override value:


This appears to be happening when using replace arguments, e.g. in the net repo:

```
./eng/common/scripts/job-matrix/Create-JobMatrix.ps1 `
-ConfigPath ./eng/pipelines/templates/stages/platform-matrix.json `
-Selection sparse `
-Replace "Pool=(.*)-general/$1-storage"
```