fix(nix): remove duplicate spirv-headers function arg (ggml-org#81)

Two well-meaning fixes both added `spirv-headers` to the package.nix
function pattern arglist (line 19 and line 22 on current HEAD), causing
a hard parse-time failure on any nix evaluation:

  error: duplicate formal function argument 'spirv-headers'
         at .devops/nix/package.nix:22:3:
             21|   shaderc,
             22|   spirv-headers,
               |   ^
             23|   useBlas ?

Drops the second occurrence. The remaining single declaration is what
the rest of the file actually references (line 19 binds the input;
`vulkanBuildInputs` and `nativeBuildInputs` consume it once each).

Reported by @cguentherTUChemnitz in ggml-org#81 (originally), then re-confirmed
by @alanscodelog on the current tip after two prior fix attempts both
landed the same line.

Verified: fixed file parses clean via nix-instantiate; injecting the
duplicate back reproduces the exact error message above.

Closes ggml-org#81.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 2 people

.devops/nix/package.nix

@@ -19,7 +19,6 @@
   spirv-headers,
   openssl,
   shaderc,
-  spirv-headers,
   useBlas ?
     builtins.all (x: !x) [
       useCuda