oh-my-posh: Update autoupdate and pre_install (#6415)

* oh-my-posh: Update autoupdate and pre_install

* Update oh-my-posh.json

---------

Co-authored-by: HUMORCE <humorce@outlook.com>

bucket/oh-my-posh.json

@@ -66,7 +66,8 @@
             }
         },
         "hash": {
-            "url": "$url.sha256"
+            "url": "$baseurl/checksums.txt",
+            "regex": "$sha256.*?$basename"
         }
     }
 }