Remove the deprecated otelhttp Client (#8266)

Author: MrAlias

CHANGELOG.md

@@ -11,6 +11,12 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ### Added
 
 - Change `Version()` function in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp` to a `const Version` string. (#8142)
+
+### Removed
+
+- The deprecated `DefaultClient`, `Get`, `Head`, `Post`, and `PostForm` in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp`.
+  Use a custom `*http.Client` with `otelhttp.NewTransport(http.DefaultTransport)` instead. (#8266)
+
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