update README for failed install of openapi2jsonschema (#2203)

* update README for failed install of openapi2jsonschema

* Fix typo

Author: myakove

class_generator/README.md

@@ -70,6 +70,15 @@ class-generator --kind Pod --add-tests
 uv tool install --python python3.9 openapi2jsonschema
 ```
 
+If install fail ([Issue 1455](https://github.com/astral-sh/uv/issues/1455)) try to install manually:
+
+```bash
+git clone https://github.com/instrumenta/openapi2jsonschema
+cd openapi2jsonschema
+sed -i s/'pyyaml = "^5.1"'/'pyyaml = ">=6.0"'/g  pyproject.toml
+uv tool install --python python3.9 .
+```
+
 - Clone this repository
 
 ```bash