Simplify codecov flag names

.codecov.yml

@@ -10,9 +10,9 @@ coverage:
 # Since Backstage is a mono repo, flags here help in getting the code coverage of individual packages.
 # Documentation: https://docs.codecov.io/docs/flags
 flags:
-  packages-core:
+  core:
     paths:
       - packages/core/
-  packages-core-api:
+  core-api:
     paths:
       - packages/core-api/

.github/workflows/master.yml

@@ -64,8 +64,8 @@ jobs:
           yarn lerna -- run test -- --coverage
           bash <(curl -s https://codecov.io/bash)
           # Upload code coverage for some specific flags. Also see .codecov.yml
-          bash <(curl -s https://codecov.io/bash) -f packages/core/coverage/* -F packages-core
-          bash <(curl -s https://codecov.io/bash) -f packages/core-api/coverage/* -F packages-core-api
+          bash <(curl -s https://codecov.io/bash) -f packages/core/coverage/* -F core
+          bash <(curl -s https://codecov.io/bash) -f packages/core-api/coverage/* -F core-api
 
       # Publishes current version of packages that are not already present in the registry
       - name: publish