[No Jira] Adjust branch names in GitHub metadata
We switched the branch names.
# specific language governing permissions and limitations
# under the License.
github:
- description: "UIMA Java SDK, version 3 (in master), 2 (in master-v2)"
+ description: "UIMA Java SDK, version 3 (in main), 2 (in main-v2)"
homepage: https://uima.apache.org
