gitlab-ci: Remove bogus cache: key on file-plug-in-tests

GNOME Infra does not enable local caching and
we don't have distributed/remote caching either.

.gitlab-ci.yml

@@ -640,10 +640,6 @@ file-plug-in-tests:
     GIMP_TESTS_DATA_FOLDER: "$CI_PROJECT_DIR/_data/gimp-test-images/"
     GIMP_TESTS_LOG_FILE: "$CI_PROJECT_DIR/_log/import-tests.log"
     REGRESSION_STRING: "Total number of regressions: 0"
-  cache:
-    key: $CI_JOB_NAME
-    paths:
-      - _data
   script:
     - API_VER=$(grep GIMP_PKGCONFIG_VERSION _build*/config.h | head -1 | sed 's/^.*"\([^"]*\)"$/\1/')
     - APP_VER=$(grep GIMP_APP_VERSION _build*/config.h | head -1 | sed 's/^.*"\([^"]*\)"$/\1/')