Change wandb env var to properly disable at start of testing (#94)

## Describe your changes

Tests are not working properly as wandb without any user logged in are
making them crash. This should not happen, since we disable WANDB with
env var when running the tests, but that variable is wrong. This is an
attempt to fix that, to make sure wandb is disabled when running tests.

## Issue Link

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## Type of change

- [x] 🐛 Bug fix (non-breaking change that fixes an issue)
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- [ ] 💥 Breaking change (fix or feature that would cause existing
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CHANGELOG.md

@@ -15,6 +15,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- Fix wandb environment variable disabling wandb during tests. Now correctly uses WANDB_MODE=disabled. [\#94](https://github.com/mllam/neural-lam/pull/94) @joeloskarsson
+
 - Fix bugs introduced with datastores functionality relating visualation plots [\#91](https://github.com/mllam/neural-lam/pull/91) @leifdenby
 
 ## [v0.2.0](https://github.com/joeloskarsson/neural-lam/releases/tag/v0.2.0)

tests/conftest.py

@@ -17,7 +17,7 @@
 
 # Disable weights and biases to avoid unnecessary logging
 # and to avoid having to deal with authentication
-os.environ["WANDB_DISABLED"] = "true"
+os.environ["WANDB_MODE"] = "disabled"
 
 DATASTORE_EXAMPLES_ROOT_PATH = Path("tests/datastore_examples")