[EDR Workflows][CI] Indicate in the name of burning specs that they're only soft failing (#172589)

## Summary

Our burn specs jobs are soft failing, but `kibana-bot` says that the
build is failed, and devs are confused.
<img
src="ef8d201f-0715-41b8-b2a9-d979fd311def"
width="400px"><img
src="f778cd2a-dff8-4451-87e9-9e561a44eafd"
width="300px">

Kibana OPS team is working on improving the status indication in
comments of `kibana-bot` in PRs (here:
https://github.com/elastic/kibana-buildkite-build-bot/pull/3).

Next to that, we could include in their name that they're soft failing,
see sample image:

<img width="1240" alt="image"
src="6775452e-bb2a-4bc0-9c5d-803b0ad33047">
<img width="928" alt="image"
src="70fdd753-4907-48d1-a0f6-56344bfa85f7">

.buildkite/pipelines/pull_request/cypress_burn.yml

@@ -1,6 +1,6 @@
 steps:
   - command: .buildkite/scripts/steps/functional/defend_workflows_burn.sh
-    label: 'Defend Workflows Cypress Tests, burning changed specs'
+    label: '[Soft fail] Defend Workflows Cypress Tests, burning changed specs'
     agents:
       queue: n2-4-virt
     depends_on: build
@@ -11,7 +11,7 @@ steps:
       automatic: false
 
   - command: .buildkite/scripts/steps/functional/defend_workflows_serverless_burn.sh
-    label: 'Defend Workflows Cypress Tests on Serverless, burning changed specs'
+    label: '[Soft fail] Defend Workflows Cypress Tests on Serverless, burning changed specs'
     agents:
       queue: n2-4-virt
     depends_on: build
@@ -22,7 +22,7 @@ steps:
       automatic: false
 
   - command: .buildkite/scripts/steps/functional/security_solution_burn.sh
-    label: 'Security Solution Cypress tests, burning changed specs'
+    label: '[Soft fail] Security Solution Cypress tests, burning changed specs'
     agents:
       queue: n2-4-spot
     depends_on: build
@@ -33,7 +33,7 @@ steps:
     soft_fail: true
 
   - command: .buildkite/scripts/steps/functional/osquery_cypress_burn.sh
-    label: 'Osquery Cypress Tests, burning changed specs'
+    label: '[Soft fail] Osquery Cypress Tests, burning changed specs'
     agents:
       queue: n2-4-spot
     depends_on: build