build(deps): bump io.camunda:spring-zeebe-starter in /spring

Bumps io.camunda:spring-zeebe-starter from 8.1.17 to 8.4.0.

---
updated-dependencies:
- dependency-name: io.camunda:spring-zeebe-starter
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

spring/pom.xml

@@ -18,7 +18,7 @@
 
 	<properties>
 		<java.version>11</java.version>
-		<spring-zeebe.version>8.1.17</spring-zeebe.version>
+		<spring-zeebe.version>8.4.0</spring-zeebe.version>
 		<zeebe.version>8.3.4</zeebe.version>
 	</properties>