Update version in plugin name

Author: AdrienVannson

docs/getting-started.md

@@ -30,5 +30,5 @@ You should now be able to compile it using:
 
 ```
 mkdir lib
-protoc -I . --python_betterproto_out=lib example.proto
+protoc -I . --python_betterproto2_out=lib example.proto
 ```

pyproject.toml

@@ -34,7 +34,7 @@ pytest = "^6.2.5"
 protobuf = "^4"
 
 [tool.poetry.scripts]
-protoc-gen-python_betterproto = "betterproto2_compiler.plugin:main"
+protoc-gen-python_betterproto2 = "betterproto2_compiler.plugin:main"
 
 [tool.ruff]
 extend-exclude = ["tests/output_*"]