i18n: add oma mirror latency clap help translation

Author: eatradish

i18n/en-US/oma.ftl

@@ -430,3 +430,4 @@ clap-download-only-help = Only download package(s) and dependency(ies) (without
 oma-mirror-up-to-date = { $mirror }: up to date
 oma-mirror-outdated = { $mirror }: outdated - { $duration }
 mirror-latency = Latency
+clap-mirror-latency-help = Test mirror synchronization latency

i18n/zh-CN/oma.ftl

@@ -421,3 +421,4 @@ clap-download-only-help = 只下载软件包和其依赖项，不安装
 oma-mirror-up-to-date = { $mirror }: 最新同步
 oma-mirror-outdated = { $mirror }: 存在延迟 - { $duration }
 mirror-latency = 延迟
+clap-mirror-latency-help = 测试镜像同步延迟

src/subcommand/mirror.rs

@@ -200,7 +200,7 @@ pub enum MirrorSubCmd {
         #[arg(long, help = fl!("clap-no-refresh-help"))]
         no_refresh: bool,
     },
-    /// Get mirrors latency
+    /// Test mirror synchronization latency
     #[command(help_template = &*HELP_TEMPLATE)]
     #[command(next_help_heading = &**crate::args::ARG_HELP_HEADING)]
     Latency {