fix: remove --skip-existing flag due to unsupported in twine 6.2.0 (#46)

twine 6.2.0 breaks upload due to unsupported feature --skip-existing 
pypa/twine#1265

Author: vasylherman

lib/publish.ts

@@ -29,7 +29,6 @@ function publishPackage(
       '--repository-url',
       repoUrl,
       '--non-interactive',
-      '--skip-existing',
       '--verbose',
       ...signArgs,
       `${distDir}/*`,