fix: bump version to v0.2.1 for next release

Updates version string in both main.ml and self_update_checker.ml
to v0.2.1 to prepare for the next release.

Removes the version fix changelog entry as this is now part of
the version bump for 0.2.1.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: vch9

src/main.ml

@@ -57,7 +57,7 @@ let ui_cmd =
 
 let root_cmd =
   let doc = "Terminal UI for managing Octez services" in
-  let info = Cmd.info "octez-manager" ~doc ~version:"0.1.1" in
+  let info = Cmd.info "octez-manager" ~doc ~version:"0.2.1" in
   Cmd.group
     info
     ~default:ui_term

src/self_update_checker.ml

@@ -10,7 +10,7 @@ open Rresult
 let ( let* ) = Result.bind
 
 (** Current version - kept in sync with main.ml *)
-let current_version = "0.2.0"
+let current_version = "0.2.1"
 
 (** GitHub repository info *)
 let github_owner = "trilitech"