chore(mobile): add description of what build ids are

Request from a customer feedback ticket (Jira: https://new-relic.atlassian.net/browse/NR-264158)

src/content/docs/mobile-monitoring/new-relic-mobile-android/install-configure/configure-new-relic-gradle-plugin.mdx

@@ -12,7 +12,6 @@ freshnessValidatedDate: never
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 The New Relic Gradle plugin extension allows you to configure the behavior of plugin tasks executed during Gradle builds. Create a plugin extension in the Gradle build files that apply the New Relic plugin, then add any of the following configuration options:
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@@ -33,7 +32,7 @@ The New Relic Gradle plugin extension allows you to configure the behavior of pl
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-        Generate unique build IDs for each app variant. Default: `true`
+        Generate unique build IDs for each app variant. Build IDs are unique identifiers assigned to each build of your app. They are helpful for tracking specific builds, especially when you have different versions with multiple builds, such as version 1.1.1 build 0.0.1. Default: `true`.
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