docs (README): run 'rpm-ostree rebase' without sudo (blue-build#183)

README.md

@@ -46,15 +46,15 @@ To rebase an existing Silverblue/Kinoite installation to the latest build:
 
 - First rebase to the unsigned image, to get the proper signing keys and policies installed:
   ```
-  sudo rpm-ostree rebase ostree-unverified-registry:ghcr.io/ublue-os/startingpoint:latest
+  rpm-ostree rebase ostree-unverified-registry:ghcr.io/ublue-os/startingpoint:latest
   ```
 - Reboot to complete the rebase:
   ```
   systemctl reboot
   ```
 - Then rebase to the signed image, like so:
   ```
-  sudo rpm-ostree rebase ostree-image-signed:docker://ghcr.io/ublue-os/startingpoint:latest
+  rpm-ostree rebase ostree-image-signed:docker://ghcr.io/ublue-os/startingpoint:latest
   ```
 - Reboot again to complete the installation
   ```
@@ -64,7 +64,7 @@ To rebase an existing Silverblue/Kinoite installation to the latest build:
 This repository builds date tags as well, so if you want to rebase to a particular day's build:
 
 ```
-sudo rpm-ostree rebase ostree-image-signed:docker://ghcr.io/ublue-os/startingpoint:20230403
+rpm-ostree rebase ostree-image-signed:docker://ghcr.io/ublue-os/startingpoint:20230403
 ```
 
 This repository by default also supports signing.