Update dependency org.openjdk.nashorn:nashorn-core to v15.7

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
org.openjdk.nashorn:nashorn-core	15.6 -> 15.7

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Release Notes

openjdk/nashorn (org.openjdk.nashorn:nashorn-core)

v15.7

Compare Source

#21 JDK-8346848 Eliminate compilation warnings with Java 21

#22 JDK-8347015 Remove support for Security Manager in Nashorn

#23 JDK-8348033 Tidy Nashorn code

#25 JDK-8349687 Some more tidying of Nashorn codebase

#26 Correct assert in ForOfLoopTreeImpl.java

License in the POM has been updated to SPDX-compliant string GNU General Public License v2.0 w/Classpath exception.

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Configuration

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[coveralls]

coverage: 80.917%. remained the same
when pulling 35966e8 on renovate/org.openjdk.nashorn-nashorn-core-15.x
into 6c7cd9f on master.