Fix go.mod and bump go version in release.yml

Author: blinktag

.github/workflows/release.yml

@@ -28,7 +28,7 @@ jobs:
         name: Set up Go
         uses: actions/setup-go@v2
         with:
-          go-version: 1.16
+          go-version: 1.21
       -
         name: Import GPG key
         id: import_gpg

go.mod

@@ -2,8 +2,6 @@ module github.com/streamdal/terraform-provider-streamdal
 
 go 1.21
 
-toolchain go1.21.5
-
 require (
 	github.com/golang/protobuf v1.5.3
 	github.com/hashicorp/terraform-plugin-docs v0.6.0