fix(cicd): Replace deprecated golangci config (#628)

# Description
This PR simply removes a deprecated config field in the golangci config
file and replaces it with its replacement. See this CICD run for an
example of a failed run:
https://github.com/caraml-dev/merlin/actions/runs/13383384346/job/37376991624#step:4:35.
Previously using the old config would only emit warnings but now they
have become explicit errors. See this PR from golangci for more details
golangci/golangci-lint#4509.

# Modifications
- `api/.golangci.yml` - Replace deprecated configs

# Tests
<!-- Besides the existing / updated automated tests, what specific
scenarios should be tested? Consider the backward compatibility of the
changes, whether corner cases are covered, etc. Please describe the
tests and check the ones that have been completed. Eg:
- [x] Deploying new and existing standard models
- [ ] Deploying PyFunc models
-->

# Checklist
- [x] Added PR label
- [ ] Added unit test, integration, and/or e2e tests
- [ ] Tested locally
- [ ] Updated documentation
- [ ] Update Swagger spec if the PR introduce API changes
- [ ] Regenerated Golang and Python client if the PR introduces API
changes

# Release Notes
<!--
Does this PR introduce a user-facing change?
If no, just write "NONE" in the release-note block below.
If yes, a release note is required. Enter your extended release note in
the block below.
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```release-note
NONE
```

Author: deadlycoconuts

api/.golangci.yml

@@ -1,9 +1,6 @@
 run:
   timeout: 10m
   modules-download-mode: readonly
-  skip-dirs:
-  - client
-  - '.*/mocks/.*'
 
 linters:
 # See https://golangci-lint.run/usage/linters/
@@ -17,3 +14,6 @@ issues:
   exclude-use-default: false
   max-issues-per-linter: 0
   max-same-issues: 0
+  exclude-dirs:
+    - client
+    - '.*/mocks/.*'