fix: updating xdebug version (#361)

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# Fixes #
updating the version for xdebug library to 2.9.0. Discussion here
flyve-mdm/docker-environment#68

### Checklist
- [x] I acknowledge that all my contributions will be made under the
project's license
- [ ] Run `make test-docker`
- [ ] Verify affected language:
- [ ] Generate [twilio-go](https://github.com/twilio/twilio-go) from our
[OpenAPI specification](https://github.com/twilio/twilio-oai) using the
[build_twilio_go.py](./examples/build_twilio_go.py) using `python
examples/build_twilio_go.py path/to/twilio-oai/spec/yaml
path/to/twilio-go` and inspect the diff
    - [ ] Run `make test` in `twilio-go`
    - [ ] Create a pull request in `twilio-go`
    - [ ] Provide a link below to the pull request
- [ ] I have made a material change to the repo (functionality, testing,
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Guidelines](https://github.com/twilio/twilio-oai-generator/blob/main/CONTRIBUTING.md)
and my PR follows them
- [ ] I have titled the PR appropriately
- [ ] I have updated my branch with the main branch
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have added the necessary documentation about the functionality
in the appropriate .md file
- [ ] I have added inline documentation to the code I modified

If you have questions, please create a GitHub Issue in this repository.

Author: kridai

examples/php/Dockerfile

@@ -6,7 +6,7 @@ RUN apt-get update -y && apt-get install -y git zip
 ENV XDEBUG_MODE=coverage
 ENV PATH="vendor/bin:$PATH"
 
-RUN pecl install xdebug
+RUN pecl install xdebug-2.9.0
 RUN pecl install pcov && docker-php-ext-enable pcov
 
 RUN git clone https://github.com/twilio/twilio-php.git twilio