workflows: drop manual go mod downloads

It's done automatically since like forever, these steps are useless.

Signed-off-by: Roman Khimov <roman@nspcc.ru>

.github/workflows/build.yml

@@ -56,9 +56,6 @@ jobs:
           go-version: '1.21'
           cache: true
 
-      - name: Update Go modules
-        run: go mod download -json
-
       - name: Build CLI
         run: make build
         env:

.github/workflows/tests.yml

@@ -102,9 +102,6 @@ jobs:
           go-version: '1.21'
           cache: true
 
-      - name: Update Go modules
-        run: go mod download -json
-
       - name: Write coverage profile
         run: go test -v ./... -coverprofile=./coverage.txt -covermode=atomic -coverpkg=./pkg...,./cli/...
 
@@ -152,8 +149,5 @@ jobs:
           go-version: '${{ matrix.go_versions }}'
           cache: true
 
-      - name: Update Go modules
-        run: go mod download -json
-
       - name: Run tests
         run: go test -v -race ./...