Update main.yml

Author: Rogger

.github/workflows/main.yml

@@ -6,7 +6,7 @@ on:
 jobs:
   build-and-test-in-docker:
     runs-on: ubuntu-22.04
-    container: ghcr.io/nrfconnect/sdk-nrf-toolchain:v2.5.0
+    container: ghcr.io/nrfconnect/sdk-nrf-toolchain:v2.6.99
     defaults:
       run:
         # Bash shell is needed to set toolchain related environment variables in docker container