Remove micromamba-version specification from workflow files

Removed all occurrences of 'micromamba-version: "1.5.10-0"' from:
- .github/workflows/mypy.yml
- .github/copilot-setup-steps.yml
- .github/workflows/test.yml

This is no longer needed as the issue (github.com/mamba-org/setup-micromamba/issues/225) has been resolved.

Co-authored-by: ricardoV94 <[email protected]>

Author: Copilot

.github/copilot-setup-steps.yml

@@ -32,7 +32,6 @@ jobs:
         uses: mamba-org/setup-micromamba@v2
         with:
           environment-name: pytensor-test
-          micromamba-version: "1.5.10-0"
           init-shell: bash
           post-cleanup: "all"
           create-args: python=3.13

.github/workflows/mypy.yml

@@ -17,7 +17,6 @@ jobs:
           persist-credentials: false
       - uses: mamba-org/setup-micromamba@v2
         with:
-          micromamba-version: "1.5.10-0" # until https://github.com/mamba-org/setup-micromamba/issues/225 is resolved
           environment-file: environment.yml
           init-shell: bash
           cache-environment: true

.github/workflows/test.yml

@@ -167,7 +167,6 @@ jobs:
         uses: mamba-org/setup-micromamba@v2
         with:
           environment-name: pytensor-test
-          micromamba-version: "1.5.10-0" # until https://github.com/mamba-org/setup-micromamba/issues/225 is resolved
           init-shell: bash
           post-cleanup: "all"
           create-args: python=${{ matrix.python-version }}
@@ -252,7 +251,6 @@ jobs:
         uses: mamba-org/setup-micromamba@v2
         with:
           environment-name: pytensor-test
-          micromamba-version: "1.5.10-0" # until https://github.com/mamba-org/setup-micromamba/issues/225 is resolved
           init-shell: bash
           post-cleanup: "all"
       - name: Install dependencies