[DOCS] Updates some references to 'master' branch to 'main'

Author: picandocodigo

docs/advanced-config.asciidoc

@@ -132,7 +132,7 @@ automatically captures client requests if you are using the agent on your code.
 If you're using `elastic-apm` v3.8.0 or up, you can set 
 `capture_elasticsearch_queries` to `true` in `config/elastic_apm.yml` to also 
 capture the body from requests in {es}. Refer to 
-https://github.com/elastic/elasticsearch-ruby/tree/master/docs/examples/apm[this example].
+https://github.com/elastic/elasticsearch-ruby/tree/main/docs/examples/apm[this example].
 
 
 [discrete]
@@ -363,7 +363,7 @@ implementing the required contract, and passing it to the client as the
 ==== Exception Handling
 
 The library defines a 
-https://github.com/elastic/elasticsearch-ruby/blob/master/elasticsearch-transport/lib/elasticsearch/transport/transport/errors.rb[number of exception classes] 
+https://github.com/elastic/elasticsearch-ruby/blob/main/elasticsearch-transport/lib/elasticsearch/transport/transport/errors.rb[number of exception classes] 
 for various client and server errors, as well as unsuccessful HTTP responses, 
 making it possible to rescue specific exceptions with desired granularity.
 

docs/examples/README.md

@@ -2,7 +2,7 @@
 
 In this directory you can find:
 
-- `apm`: A practical example of integrating elasticsearch-ruby and [Elastic APM](https://www.elastic.co/apm) with the [Ruby APM Agent](https://github.com/elastic/apm-agent-ruby). See the [the README](https://github.com/elastic/elasticsearch-ruby/tree/master/docs/examples/apm/README.md#observability-example).
+- `apm`: A practical example of integrating elasticsearch-ruby and [Elastic APM](https://www.elastic.co/apm) with the [Ruby APM Agent](https://github.com/elastic/apm-agent-ruby). See the [the README](https://github.com/elastic/elasticsearch-ruby/tree/main/docs/examples/apm/README.md#observability-example).
 - `guide`: Contains the generated Ruby code examples for the [Elasticsearch Reference](https://www.elastic.co/guide/en/elasticsearch/reference/current/index.html).
 - `percolator`: An example using a percolator in Elasticsearch version 5.x and higher.
 - `rabbitmq`: Example of indexing the payload of a RabbitMQ queue.

docs/overview.asciidoc

@@ -26,10 +26,10 @@ More documentation is hosted in https://github.com/elastic/elasticsearch-ruby[Gi
 
 The `elasticsearch` gem combines two separate Rubygems:
 
-* https://github.com/elastic/elasticsearch-ruby/tree/master/elasticsearch-transport[`elasticsearch-transport`]
+* https://github.com/elastic/elasticsearch-ruby/tree/main/elasticsearch-transport[`elasticsearch-transport`]
 provides an HTTP Ruby client for connecting to the {es} cluster,
 
-* https://github.com/elastic/elasticsearch-ruby/tree/master/elasticsearch-api[`elasticsearch-api`]
+* https://github.com/elastic/elasticsearch-ruby/tree/main/elasticsearch-api[`elasticsearch-api`]
 provides a Ruby API for the {es} RESTful API.
 
 Please consult their respective documentation for configuration options and 

elasticsearch-api/utils/README.md

@@ -2,7 +2,7 @@
 
 ## The Generator
 
-This directory hosts The Generator, a tool that generates the classes for each API endpoint from the [Elasticsearch REST API JSON Specification](https://github.com/elastic/elasticsearch/tree/master/rest-api-spec).
+This directory hosts The Generator, a tool that generates the classes for each API endpoint from the [Elasticsearch REST API JSON Specification](https://github.com/elastic/elasticsearch/tree/main/rest-api-spec).
 
 ### Generate