ci: add libssh2-1-dev system dependency for Net::SSH2 compilation

The CI was failing because Net::SSH2 Perl module requires libssh2-1-dev
system library to compile. Added installation of this dependency in the
GitHub Actions workflow before Perl module installation.

Author: josecelano

.github/workflows/testing.yml

@@ -42,6 +42,11 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v4
 
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libssh2-1-dev
+
       - name: Install Perl and dependencies
         run: |
           # Ubuntu already has Perl 5.34+ installed