Update version in README

Author: carmenbianca

README.md

@@ -46,7 +46,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: REUSE Compliance Check
-        uses: fsfe/reuse-action@v5
+        uses: fsfe/reuse-action@v6
 ```
 
 If you would like to run other subcommands, you could use the following snippet which outputs a the SPDX bill of materials:
@@ -55,7 +55,7 @@ If you would like to run other subcommands, you could use the following snippet
       - name: Checkout
         uses: actions/checkout@v4
       - name: REUSE SPDX SBOM
-        uses: fsfe/reuse-action@v5
+        uses: fsfe/reuse-action@v6
         with:
           args: spdx
 ```
@@ -66,7 +66,7 @@ In the same fashion, it is possible to add optional arguments like `--include-su
       - name: Checkout
         uses: actions/checkout@v4
       - name: REUSE Compliance Check
-        uses: fsfe/reuse-action@v5
+        uses: fsfe/reuse-action@v6
         with:
           args: --include-submodules lint
 ```