Try updating core files prior to maven build

Signed-off-by: Taylor Smock <smocktaylor@gmail.com>

Author: tsmock

.github/workflows/ant.yml

@@ -165,6 +165,7 @@ jobs:
       run: |
         set -ex
         cd $GITHUB_WORKSPACE/josm/plugins/${{ inputs.plugin-directory }}
+        svn up ../../core
         ls ../..
         ls ../../core
         ls ../../core/tools

.github/workflows/internal_ant.yml

@@ -165,6 +165,7 @@ jobs:
       run: |
         set -ex
         cd $GITHUB_WORKSPACE/josm/plugins/${{ inputs.plugin-directory }}
+        svn up ../../core
         ls ../..
         ls ../../core
         ls ../../core/tools