fix: remove maven-plugin from release-please-config for invoker/conformance/pom.xml (#322)

Previous change d31b502 incorrectly added an extra file to the invoker
release which is causing automation breakages when the invoker release
PRs are created.

Move config to the right package.

Author: maemayve

.github/release-please-config.json

@@ -46,11 +46,6 @@
                     "path": "conformance/pom.xml",
                     "xpath": "//*[local-name()='artifactId' and text()='conformance']/parent::*/*[local-name()='version']"
                 },
-                {
-                    "type": "xml",
-                    "path": "conformance/pom.xml",
-                    "xpath": "//*[local-name()='artifactId' and text()='function-maven-plugin']/parent::*/*[local-name()='version']" 
-                },
                 {
                     "type": "xml",
                     "path": "testfunction/pom.xml",