amazon-image: Remove tags from label, use version only

By default, `system.nixos.label` includes `system.nixos.tags` which
historically was not set for the amazon image.

Keeping the tag in the label of the generated disk image inside the
derivation (i.e. `image.filePath`) makes it easier to tell that the
file is for amazon (i.e.
`nixos-image-amazon-25.11pre-git-x86_64-linux.vpc`) while the "label"
in `image-info.json` for users of the AWS api stays stable (i.e.
`/25.05pre-git-x86_64-linux`).

`

Author: phaer

nixos/maintainers/scripts/ec2/amazon-image.nix

@@ -140,15 +140,15 @@ in
            echo "file ${cfg.format} $rootDisk" >> $out/nix-support/hydra-build-products
 
           ${pkgs.jq}/bin/jq -n \
-            --arg system_label ${lib.escapeShellArg config.system.nixos.label} \
+            --arg system_version ${lib.escapeShellArg config.system.nixos.version} \
             --arg system ${lib.escapeShellArg pkgs.stdenv.hostPlatform.system} \
             --arg root_logical_bytes "$(${pkgs.qemu_kvm}/bin/qemu-img info --output json "$rootDisk" | ${pkgs.jq}/bin/jq '."virtual-size"')" \
             --arg boot_logical_bytes "$(${pkgs.qemu_kvm}/bin/qemu-img info --output json "$bootDisk" | ${pkgs.jq}/bin/jq '."virtual-size"')" \
             --arg boot_mode "${amiBootMode}" \
             --arg root "$rootDisk" \
             --arg boot "$bootDisk" \
            '{}
-             | .label = $system_label
+             | .label = $system_version
              | .boot_mode = $boot_mode
              | .system = $system
              | .disks.boot.logical_bytes = $boot_logical_bytes
@@ -181,13 +181,13 @@ in
            echo "file ${cfg.format} $diskImage" >> $out/nix-support/hydra-build-products
 
           ${pkgs.jq}/bin/jq -n \
-            --arg system_label ${lib.escapeShellArg config.system.nixos.label} \
+            --arg system_version ${lib.escapeShellArg config.system.nixos.version} \
             --arg system ${lib.escapeShellArg pkgs.stdenv.hostPlatform.system} \
             --arg logical_bytes "$(${pkgs.qemu_kvm}/bin/qemu-img info --output json "$diskImage" | ${pkgs.jq}/bin/jq '."virtual-size"')" \
             --arg boot_mode "${amiBootMode}" \
             --arg file "$diskImage" \
              '{}
-             | .label = $system_label
+             | .label = $system_version
              | .boot_mode = $boot_mode
              | .system = $system
              | .logical_bytes = $logical_bytes