feat(nimbus): Upgrade 24.12.0 -> 25.1.0

Remove the `nimble.nix` patch as on version 25.1.0 there is no need to
patch `nimble.nix` as it contains the correct hash. I verified it like
this:

```
nurl -S https://github.com/nim-lang/nimble 123f97a5e4ee9ba35720c0869e19a047c43c797e
$ nix flake prefetch --extra-experimental-features 'nix-command flakes' --json git+https://github.com/nim-lang/nimble?allRefs=1&rev=123f97a5e4ee9ba35720c0869e19a047c43c797e&submodules=1
fetchFromGitHub {
  owner = "nim-lang";
  repo = "nimble";
  rev = "123f97a5e4ee9ba35720c0869e19a047c43c797e";
  hash = "sha256-Rz48sGUKZEAp+UySla+MlsOfsERekuGKw69Tm11fDz8=";
  fetchSubmodules = true;
}
```

The hash `sha256-Rz48sGUKZEAp+UySla+MlsOfsERekuGKw69Tm11fDz8=` is
exactly the same as the one in nimble.nix @ 25.1.0:
https://github.com/status-im/nimbus-eth2/blob/v25.1.0/nix/nimble.nix#L12

Author: galin-s

pkgs/nimbus/default.nix

@@ -1,20 +1,16 @@
 {
-  applyPatches,
   fetchFromGitHub,
   pkgs,
   targets ? ["nimbus_beacon_node" "nimbus_validator_client" "gnosis-build" "gnosis-vc-build"],
   stableSystems ? ["x86_64-linux" "aarch64-linux"],
 }: let
-  version = "24.12.0";
-  src = applyPatches {
-    src = fetchFromGitHub {
-      owner = "status-im";
-      repo = "nimbus-eth2";
-      rev = "v${version}";
-      hash = "sha256-DBvsnGr91a69eCj1hAeoVOpxas5rfaT36rIxWEmvIVg=";
-      fetchSubmodules = true;
-    };
-    patches = [./fix-hash.patch];
+  version = "25.1.0";
+  src = fetchFromGitHub {
+    owner = "status-im";
+    repo = "nimbus-eth2";
+    rev = "v${version}";
+    hash = "sha256-kTpEN4bw/Pp2J4FEfHOEUMwBbEybVp7nhie4P3IHAnY=";
+    fetchSubmodules = true;
   };
 in
   import "${src}/nix" {inherit pkgs targets stableSystems;}