make sure expect is installed on ubuntu runners

.github/workflows/linux_ci.yml

@@ -124,6 +124,7 @@ jobs:
           ## The following is needed for examples/wkhtmltopdf.v
           wget https://github.com/wkhtmltopdf/packaging/releases/download/0.12.6-1/wkhtmltox_0.12.6-1.focal_amd64.deb
           sudo apt-get install --quiet -y xfonts-75dpi xfonts-base
+          sudo apt-get install --quiet -y expect
           sudo dpkg -i wkhtmltox_0.12.6-1.focal_amd64.deb
       - name: Build v
         run: |
@@ -175,6 +176,7 @@ jobs:
           sudo apt-get update
           sudo apt-get install --quiet -y postgresql libpq-dev libssl-dev sqlite3 libsqlite3-dev valgrind
           sudo apt-get install --quiet -y libfreetype6-dev  libxi-dev libxcursor-dev libgl-dev
+          sudo apt-get install --quiet -y expect
       - name: Build V
         run: make -j4 && ./v -cc gcc -cg -cstrict -o v cmd/v
       - name: Valgrind v.c
@@ -286,6 +288,7 @@ jobs:
           sudo apt-get update
           sudo apt-get install --quiet -y postgresql libpq-dev libssl-dev sqlite3 libsqlite3-dev valgrind
           sudo apt-get install --quiet -y libfreetype6-dev  libxi-dev libxcursor-dev libgl-dev
+          sudo apt-get install --quiet -y expect
           sudo apt-get install --quiet -y clang
       - name: Build V
         run: make -j4 && ./v -cc clang -cg -cstrict -o v cmd/v