Bump go.opentelemetry.io/build-tools/issuegenerator from 0.8.0 to 0.15.0 in /internal/tools #27435

Job	Run time
govulncheck (receiver-0)	1m 30s
govulncheck (receiver-1)	1m 30s
govulncheck (processor)	1m 20s
govulncheck (exporter)	1m 26s
setup-environment	0s
govulncheck (extension)	1m 27s
govulncheck (connector)	1m 25s
govulncheck (internal)	1m 27s
govulncheck (pkg)	1m 23s
check-codeowners	0s
check-collector-module-version	0s
checks	0s
lint-matrix	0s
correctness-traces	0s
build-examples	0s
correctness-metrics	0s
integration-tests	0s
unittest-matrix	0s
lint	0s
unittest	0s
cross-compile	0s
coverage	0s
build-package	0s
windows-msi	0s
publish-check	0s
publish-dev	0s
publish-stable	0s
rotate-milestone	0s
	11m 28s

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