Clarify user fields in span protocol documentation (#16588)

Updated user-related fields to remove 'gated by sendDefaultPii' notes
for clarity. SDKs gate any automatic `scope.setUser()` calls instead.

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Co-authored-by: Ivana Kellyer <ivana.kellyer@sentry.io>

Author: cleptric

develop-docs/sdk/telemetry/spans/span-protocol.mdx

@@ -174,10 +174,10 @@ Empty attributes must be omitted.
 | `sentry.replay_id` | string | The id of the currently running replay (if available) |
 | `os.name` | string | The operating system name (e.g., "Linux", "Windows", "macOS") |
 | `browser.name` | string | The browser name (e.g., "Chrome", "Firefox", "Safari") |
-| `user.id` | string | The user ID (gated by `sendDefaultPii`) |
-| `user.email` | string | The user email (gated by `sendDefaultPii`) |
-| `user.ip_address` | string | The user IP address (gated by `sendDefaultPii`) |
-| `user.name` | string | The user username (gated by `sendDefaultPii`) |
+| `user.id` | string | The user ID |
+| `user.email` | string | The user email |
+| `user.ip_address` | string | The user IP address |
+| `user.name` | string | The user username |
 | `thread.id` | string | The thread ID |
 | `thread.name` | string | The thread name |
 | `sentry.sdk.name` | string | Name of the Sentry SDK (e.g., "sentry.php", "sentry.javascript") |