vimPlugins.elixir-tools-nvim: fix credo-language-server (#275505)

Credo language server gets broken by patchShebangs in its current form.

-S without a command in the path causes the 'elixir' part of this
shebang to be removed. This is because the following line defaults to
'true', which produces a blank string:

b0d1fe9a32/pkgs/build-support/setup-hooks/patch-shebangs.sh (L91)

pkgs/applications/editors/vim/plugins/overrides.nix

@@ -549,6 +549,12 @@
       '';
   });
 
+  elixir-tools-nvim = super.elixir-tools-nvim.overrideAttrs {
+    fixupPhase = ''
+      patchShebangs $(find $out/bin/ -type f -not -name credo-language-server)
+    '';
+  };
+
   executor-nvim = super.executor-nvim.overrideAttrs {
     dependencies = with self; [ nui-nvim ];
   };