Revert formatting changes in osx.yml and xhalf_float_impl.hpp

- Reset indentation in .github/workflows/osx.yml to original style
- Restore trailing spaces in include/xtl/xhalf_float_impl.hpp
- Keep only meaningful code changes: macos version update, [[maybe_unused]] attribute

Author: gouarin

.github/workflows/osx.yml

@@ -16,31 +16,31 @@ jobs:
           - 15
           - 26
     runs-on: macos-${{ matrix.os }}
-    name: "macos-${{ matrix.os }}"
+    name: 'macos-${{ matrix.os }}'
 
     steps:
-      - name: Checkout code
-        uses: actions/checkout@v3
+    - name: Checkout code
+      uses: actions/checkout@v3
 
-      - name: Set mamba environment
-        uses: mamba-org/setup-micromamba@v1
-        with:
-          environment-file: environment-dev.yml
-          cache-environment: true
+    - name: Set mamba environment
+      uses: mamba-org/setup-micromamba@v1
+      with:
+        environment-file: environment-dev.yml
+        cache-environment: true
 
-      - name: Configure
-        shell: bash -l {0}
-        run: |
-          mkdir -p build
-          cd build
-          cmake .. -DBUILD_TESTS=ON \
-                   -GNinja
+    - name: Configure
+      shell: bash -l {0}
+      run: |
+        mkdir -p build
+        cd build
+        cmake .. -DBUILD_TESTS=ON \
+                 -GNinja
 
-      - name: Build
-        shell: bash -l {0}
-        run: ninja -C build test_xtl
+    - name: Build
+      shell: bash -l {0}
+      run: ninja -C build test_xtl
 
-      - name: Test
-        run: |
-          cd build/test
-          ./test_xtl
+    - name: Test
+      run: |
+        cd build/test
+        ./test_xtl