Update group_name regular expression to match matrix builds

What does this MR do?

Related to #230452 (closed) and continues !39985 (merged)

Screenshots

Using the CI config defined at: #230452 (comment 400072357)

Pasted here for easier access

image: alpine:latest
# Matrix Example 
    
stages:
    - build
    - test
    - deploy


# Matrix builds
build-matrix:
    stage: build
    script:
        - echo "Build started for distribution $DISTRIBUTION with architecture $ARCHITECTURE on target $TARGET"
    parallel:
        matrix:
            - ARCHITECTURE: [x86, x64]
              TARGET: [debug, release]
              DISTRIBUTION: [rhel8, ubuntu20, debian10, sles125, opensuse152, fedora32]

test-matrix:
    stage: test
    script:
        - echo "Test started for distribution $DISTRIBUTION with architecture $ARCHITECTURE on target $TARGET"    
    parallel:
        matrix:
            - ARCHITECTURE: [x86, x64]
              TARGET: [release]
              DISTRIBUTION: [rhel8, ubuntu20, debian10, sles125, opensuse152, fedora32]

deploy-matrix:
    stage: deploy
    script:
        - echo "Deploy started for distribution $DISTRIBUTION with architecture $ARCHITECTURE on target $TARGET"    
    parallel:
        matrix:
            - ARCHITECTURE: [x86, x64]
              TARGET: [release]
              DISTRIBUTION: [rhel8, ubuntu20, debian10, sles125, opensuse152, fedora32]

Before image:

After image:

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team