fix(spanner): remove explicit tink version to resolve dependency convergence conflict (googleapis#13602)

This PR removes the explicit Tink version declaration inside
`java-spanner/google-cloud-spanner/pom.xml` to allow it to use the
managed version from `third-party-dependencies/pom.xml`. This resolves
the dependency convergence check failures in the CI.

Author: jinseopkim0

java-spanner/google-cloud-spanner/pom.xml

@@ -539,7 +539,6 @@
     <dependency>
       <groupId>com.google.crypto.tink</groupId>
       <artifactId>tink</artifactId>
-      <version>1.13.0</version>
     </dependency>
   </dependencies>
   <profiles>