Removing README.md segment that is no longer relevant

Author: dabico

README.md

@@ -68,19 +68,6 @@ To use in your own Maven project, include the following in your POM file:
 </dependency>
 ```
 
-## Adding a grammar
-
-To add a new grammar, first create a submodule in the repository root:
-
-```shell
-git submodule add https://github.com/{{owner}}/tree-sitter-{{language}}.git tree-sitter-{{language}}
-```
-
-Once finished, check out the release whose version is **less than or equal** to the current `tree-sitter` release:
-```shell
-(cd tree-sitter-{{language}} && git checkout {{version}})
-```
-
 ## Example usage
 
 First, load the shared object somewhere in your application: