refactor(dialog): remove unused custom properties

* removes two unused custom properties:
  `--spectrum-dialog-confirm-max-inline-size`
  `--spectrum-dialog-confirm-max-height`

Those have been in the repo for quite some time, but have never been used in Spectrum CSS itself.

Author: pfulton

components/dialog/index.css

@@ -21,8 +21,6 @@ governing permissions and limitations under the License.
   --spectrum-dialog-confirm-small-width: 400px;
   --spectrum-dialog-confirm-medium-width: 480px;
   --spectrum-dialog-confirm-large-width: 640px;
-  --spectrum-dialog-confirm-max-inline-size: 90vw;
-  --spectrum-dialog-confirm-max-height: 90vh;
   --spectrum-dialog-confirm-divider-block-spacing-start: var(--spectrum-spacing-300);
   --spectrum-dialog-confirm-divider-block-spacing-end: var(--spectrum-spacing-200);
   --spectrum-dialog-confirm-description-text-color: var(--spectrum-gray-800);
@@ -382,4 +380,4 @@ governing permissions and limitations under the License.
   .spectrum-Dialog {
     border: solid;
   }
-}
+}