Bump org.apache.maven.plugins:maven-assembly-plugin in /spec

Bumps [org.apache.maven.plugins:maven-assembly-plugin](https://github.com/apache/maven-assembly-plugin) from 3.3.0 to 3.8.0.
- [Release notes](https://github.com/apache/maven-assembly-plugin/releases)
- [Commits](https://github.com/apache/maven-assembly-plugin/compare/maven-assembly-plugin-3.3.0...v3.8.0)

---
updated-dependencies:
- dependency-name: org.apache.maven.plugins:maven-assembly-plugin
  dependency-version: 3.8.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

spec/pom.xml

diff --git a/spec/pom.xml b/spec/pom.xml
index d21434b..1ad2a66 100644
--- a/spec/pom.xml
+++ b/spec/pom.xml
@@ -181,7 +181,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-assembly-plugin</artifactId>
-                <version>3.3.0</version>
+                <version>3.8.0</version>
                 <inherited>false</inherited>
                 <executions>
                     <execution>