[fix] Complete comment on ProducerInterceptor interface BeforeSend method

[ojcm]

Motivation

The comment against the BeforeSend method in the ProducerInterceptor interface is incomplete. Whilst it's fairly easy to infer the missing words, the comment is clearer when complete.

pulsar-client-go/pulsar/producer_interceptor.go

Lines 21 to 22 in af56e60

	// BeforeSend This is called before send the message to the brokers. This method is allowed to modify the
	BeforeSend(producer Producer, message *ProducerMessage)

Modifications

Completed the comment so it reads

// BeforeSend This is called before send the message to the brokers. This method is allowed to modify the
// message.

Verifying this change

• Make sure that the change passes the CI checks.

This change is a trivial rework / code cleanup without any test coverage.

This is the first time I've come across these interceptors so I've verified that the BeforeSend method can modify the message: https://go.dev/play/p/UQ4Q1MNPOpf

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API: no
• The schema: no
• The default values of configurations: no
• The wire protocol: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable
• If a feature is not applicable for documentation, explain why? It is the documentation.
• If a feature is not documented yet in this PR, please create a followup issue for adding the documentation

[tisonkun]

Thank you!