Fix inverted fixed-size guard in FixedSizeSortedMap.putAll

[rootvector2]

putAll inverted the isSubCollection check so it rejected legal value updates and let a new key grow the fixed-size map; negate it to match sibling FixedSizeMap.putAll, spotted while auditing the fixed-size decorators.

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[Copilot]

Pull request overview

Fixes FixedSizeSortedMap.putAll to correctly reject inserts of new keys into a fixed-size map while still allowing value updates for existing keys, aligning behavior with the fixed-size decorator contract and the sibling FixedSizeMap.putAll.

Changes:

• Invert the CollectionUtils.isSubCollection guard in FixedSizeSortedMap.putAll so only new keys are rejected.
• Add a focused JUnit test covering: existing-key updates, empty putAll no-op, and rejection of new keys without growing the map.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/main/java/org/apache/commons/collections4/map/FixedSizeSortedMap.java	Corrects putAll guard condition to prevent adding new keys to a fixed-size sorted map.
src/test/java/org/apache/commons/collections4/map/FixedSizeSortedMapTest.java	Adds regression test ensuring putAll allows updates but rejects new keys and preserves size.

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