Switch release workflows to shared main branch

Use pc-nrfconnect-shared main branch to handle release-app
workflows.

Signed-off-by: Arkadiusz Balys <arkadiusz.balys@nordicsemi.no>

Author: ArekBalysNordic

.github/workflows/release-latest.yml

@@ -6,7 +6,7 @@ on:
 
 jobs:
     release:
-        uses: NordicSemiconductor/pc-nrfconnect-shared/.github/workflows/release-app.yml@v215
+        uses: NordicSemiconductor/pc-nrfconnect-shared/.github/workflows/release-app.yml@main
         with:
             source: latest (internal)
         secrets: inherit

.github/workflows/release.yml

@@ -19,7 +19,7 @@ on:
 
 jobs:
     release:
-        uses: NordicSemiconductor/pc-nrfconnect-shared/.github/workflows/release-app.yml@v215
+        uses: NordicSemiconductor/pc-nrfconnect-shared/.github/workflows/release-app.yml@main
         with:
             source: ${{ inputs.source }}
             ref: ${{ inputs.ref }}