Update actions/cache action to v6

Author: renovate[bot]

.github/workflows/main.yml

@@ -37,7 +37,7 @@ jobs:
     - name: Checkout
       uses: actions/checkout@v7
     - name: NuGet cache
-      uses: actions/cache@v5
+      uses: actions/cache@v6
       with:
         key: ${{ runner.os }}.nuget.${{ hashFiles('**/*.fsproj') }}
         path: ${{ env.NUGET_PACKAGES }}
@@ -76,7 +76,7 @@ jobs:
     - name: Set up .NET SDK
       uses: actions/setup-dotnet@v5
     - name: NuGet cache
-      uses: actions/cache@v5
+      uses: actions/cache@v6
       with:
         key: ${{ runner.os }}.nuget.${{ hashFiles('**/*.fsproj') }}
         path: ${{ env.NUGET_PACKAGES }}

.github/workflows/release.yml

@@ -35,7 +35,7 @@ jobs:
     - name: Set up .NET SDK
       uses: actions/setup-dotnet@v5
     - name: NuGet cache
-      uses: actions/cache@v5
+      uses: actions/cache@v6
       with:
         key: ${{ runner.os }}.nuget.${{ hashFiles('**/*.fsproj') }}
         path: ${{ env.NUGET_PACKAGES }}