codecov: update config file

Delete dead entries from the codecov config file.
There is no more dtl in the repo, it was removed a long
time ago. Also the cannon directory in the contracts
has tests, so remove ignoring it.

codecov.yml

@@ -4,7 +4,6 @@ ignore:
   - "**/*.t.sol"
   - "op-bindings/bindings/*.go"
   - "packages/contracts-bedrock/contracts/vendor/WETH9.sol"
-  - "packages/contracts-bedrock/contracts/cannon"  # tested through Go tests
   - 'packages/contracts-bedrock/contracts/EAS/**/*.sol'
 coverage:
   status:
@@ -31,6 +30,5 @@ flag_management:
     - name: common-ts-tests
     - name: contracts-tests
     - name: core-utils-tests
-    - name: dtl-tests
     - name: chain-mon-tests
     - name: sdk-tests