servarr-ffmpeg.tests: fix the eval

Without the change the eval fails as:

    $ nix build --no-link -f. servarr-ffmpeg.tests
    error:
       … while calling the 'derivationStrict' builtin
         at <nix/derivation-internal.nix>:37:12:
           36|
           37|   strict = derivationStrict drvAttrs;
             |            ^
           38|

       … while evaluating derivation 'check-meta-pkg-config-modules-for-servarr-ffmpeg-5.1.4'
         whose name attribute is located at pkgs/stdenv/generic/make-derivation.nix:468:13

       … while evaluating attribute 'buildCommand' of derivation 'check-meta-pkg-config-modules-for-servarr-ffmpeg-5.1.4'
         at pkgs/build-support/trivial-builders/default.nix:80:17:
           79|         enableParallelBuilding = true;
           80|         inherit buildCommand name;
             |                 ^
           81|         passAsFile = [ "buildCommand" ] ++ (derivationArgs.passAsFile or [ ]);

       (stack trace truncated; use '--show-trace' to show the full, detailed trace)

       error: attribute 'pkgConfigModules' missing
       at pkgs/build-support/testers/testMetaPkgConfig/tester.nix:17:35:
           16|   ''
           17|     echo "found all of ${toString package.meta.pkgConfigModules}" > "$out"
             |                                   ^
           18|   ''

0 files changed, 0 insertions, 0 deletions