[chore] Remove references to component.UseLocalHostAsDefaultHost (#11773)

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#### Description

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Follows #11235, relates to #8510

Author: mx-psi

docs/security-best-practices.md

@@ -148,9 +148,6 @@ receivers:
 Generally, `localhost`-like addresses should be preferred over the 0.0.0.0 address.
 For more information, see [CWE-1327](https://cwe.mitre.org/data/definitions/1327.html).
 
-To change the default endpoint to be `localhost`-bound in all components, enable the `component.UseLocalHostAsDefaultHost` feature gate. This feature gate will be enabled by default in the Collector in a future release.
-
-
 If `localhost` resolves to a different IP due to your DNS settings then explicitly use the loopback IP instead: `127.0.0.1` for IPv4 or `::1` for IPv6. In IPv6 setups, ensure your system supports both IPv4 and IPv6 loopback addresses to avoid issues.
 
 Using `localhost` may not work in environments like Docker, Kubernetes, and other environments that have non-standard networking setups.  We've documented a few working example setups for the OTLP receiver gRPC endpoint below, but other receivers and other Collector components may need similar configuration.
@@ -324,4 +321,4 @@ Extensions may also be used to run subprocesses. This can be useful when
 collection mechanisms that cannot natively be run by the Collector (e.g.
 FluentBit). Subprocesses expose a completely separate attack vector that would
 depend on the subprocess itself. In general, care should be taken before
-running any subprocesses alongside the Collector.
+running any subprocesses alongside the Collector.

receiver/otlpreceiver/README.md

@@ -40,9 +40,9 @@ The following settings are configurable:
 
 - `endpoint` (default = localhost:4317 for grpc protocol, localhost:4318 http protocol):
   host:port to which the receiver is going to receive data. The valid syntax is
-  described at https://github.com/grpc/grpc/blob/master/doc/naming.md. The
-  `component.UseLocalHostAsDefaultHost` feature gate changes these to localhost:4317 and
-  localhost:4318 respectively. This will become the default in a future release.
+  described at https://github.com/grpc/grpc/blob/master/doc/naming.md. See our 
+  [security best practices doc](https://opentelemetry.io/docs/security/config-best-practices/#protect-against-denial-of-service-attacks)
+  to understand how to set the endpoint in different environments.
 
 ## Advanced Configuration