[feat] Bumps Vault version to 1.15.0 (#8)

rockcraft.yaml

@@ -1,7 +1,7 @@
 name: vault
 base: bare
 build-base: ubuntu:22.04
-version: "1.14.3"
+version: "1.15.0"
 summary: A ROCK container image for Vault
 description: |
   A ROCK container image for Vault, a tool for secrets management, encryption as a service, and privileged access management.
@@ -20,12 +20,12 @@ parts:
   vault:
     plugin: go
     source: https://github.com/hashicorp/vault.git
-    source-tag: v1.14.3
+    source-tag: v1.15.0
     source-type: git
     stage:
       - bin/vault
     build-snaps:
-      - go/1.20/stable
+      - go/1.21/stable
 
   default-config:
     plugin: dump