fix misnamed partial include tag in docs

Resolves warning message:

> asciidoctor: WARNING: src/spec/doc/core-semantics.adoc: line 691: tag 'stc_assign_array_fail' not found in include file: /home/dallen/projects/asciidoctor/use-cases/groovy-core/src/spec/test/typing/TypeCheckingTest.groovy