[Obs Onboarding][Auto Detect] Fix auto detect script failing on systems with older curl versions (#214552)

Closes https://github.com/elastic/kibana/issues/212075

This change replaces the `--no-progress-meter` curl parameter with a
combination of `--silent` and `--show-error` to suppress verbose
progress output. `--no-progress-meter` was introduced in curl `v7.67.0`
which is not available on some popular OSs like RHEL 8.

## How to test

1. Create an RHEL 8 instance in GCP and login via SSH
2. Open auto detect flow on the Kibana instance deployed from this PR
3. Go through the flow and make sure the auto detect script goes through
all steps successfully

x-pack/solutions/observability/plugins/observability_onboarding/public/assets/auto_detect.sh

@@ -112,7 +112,8 @@ update_step_progress() {
     --header "x-elastic-internal-origin: Kibana" \
     --data "$data" \
     --output /dev/null \
-    --no-progress-meter \
+    --silent \
+    --show-error \
     --fail
 }
 
@@ -288,7 +289,8 @@ install_integrations() {
     --header "kbn-xsrf: true" \
     --header "x-elastic-internal-origin: Kibana" \
     --data "$(echo -e "$install_integrations_api_body_string")" \
-    --no-progress-meter \
+    --silent \
+    --show-error \
     --fail \
     --output "$elastic_agent_tmp_config_path"