`s3_path` param does not expect trailing slash for files/folders

[jacobtabak]

The default value of s3_path for APKs and IPAs is "#{version_code}_#{version_name}/" unless s3_path

The default value of s3_path for files is "files" unless s3_path

You can see that for APKs, a trailing slash is expected, and for files, it is not. This means that files get uploaded to subdirectory (with a 0-length title) of the directory that the APKs/IPAs get uploaded to.

For reference, this is what our invocation looks like -

    aws_s3(
      access_key: ENV['AWS_ACCESS_KEY_ID'],
      secret_access_key: ENV['AWS_SECRET_ACCESS_KEY'],
      bucket: ENV['ARTIFACTS_S3_BUCKET'],
      region: "eu-west-1",
      files: [ 
        "#{lane_context[SharedValues::GRADLE_AAB_OUTPUT_PATH]}" 
      ],
      path: "#{ENV["CIRCLE_BUILD_NUM"]}",
      app_directory: artifacts_root + "prod/android",
      upload_metadata: true
    )