ref(js): Add note about old name of HttpContext integration (#5099)

Adds a note to the HttpContext integration of the JS SDK explaining that it was called UserAgent before v7. This ensures that pre-v7 users can find correct information about their default integrations.

Author: Lms24

src/platforms/javascript/common/configuration/integrations/default.mdx

@@ -1,7 +1,7 @@
 ---
 title: Default Integrations
 excerpt: ""
-description: "Learn more about system integrations Dedupe, InboundFilters, FunctionToString, Breadcrumbs, GlobalHandlers, LinkedErrors, and HttpContext, that are enabled by default to integrate into the standard library or the interpreter itself."
+description: "Learn more about system integrations Dedupe, InboundFilters, FunctionToString, Breadcrumbs, GlobalHandlers, LinkedErrors, and HttpContext (UserAgent), that are enabled by default to integrate into the standard library or the interpreter itself."
 redirect_from:
   - /platforms/javascript/integrations/default/
   - /platforms/javascript/default-integrations/
@@ -122,10 +122,19 @@ document
   });
 ```
 
-### HttpContext
+### HttpContext (previously: UserAgent)
 
 _Import name: `Sentry.Integrations.HttpContext`_
 
+<Note>
+
+Before version 7.0.0 of the Sentry SDK, this integration was called `UserAgent`.
+It was renamed because the integration handles more than just user-agent data.
+
+_Import name: `Sentry.Integrations.UserAgent`_
+
+</Note>
+
 This integration attaches HTTP request information, such as URL, user-agent, referrer and other headers to the event.
 It allows us to correctly catalog and tag events with specific OS, browser, and version information.