build: configure subproject sysprof with -Dagent=false

Sysprof has a new -Dagent=true build option which allows installing a
/usr/bin/sysprof-agent program (simimlar to sysprof-cli). It provides a
P2P D-Bus API to the process which can control subprocesses. It's used by
IDE tooling to have more control across container boundaries.

However, we do not need it for GTK CI.

meson.build

@@ -670,6 +670,7 @@ if not get_option('sysprof').disabled()
   libsysprof_capture_dep = dependency('sysprof-capture-4', version: sysprof_req,
     required: get_option('sysprof'),
     default_options: [
+      'agent=false',
       'examples=false',
       'gtk=false',
       'tests=false',
@@ -684,6 +685,7 @@ if not get_option('sysprof').disabled()
   libsysprof_dep = dependency('sysprof-4',
     required: false,
     default_options: [
+      'agent=false',
       'examples=false',
       'gtk=false',
       'tests=false',