Add space between type and variable

[petersmythe]

Fixes: [storage.DefaultStorageFinder] - Found system environment variableGEOSERVER_DATA_DIR set to

Checklist

• I have read the contribution guidelines.
• I have sent a Contribution Licence Agreement (not required for small changes, e.g., fixing typos in documentation).
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For core and extension modules:

• New unit tests have been added covering the changes.
• Documentation has been updated (if change is visible to end users).
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• There is an issue in the GeoServer Jira (except for changes that do not affect administrators or end users in any way).
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