chore(deps): update dependency eventsource to v4

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.changeset/renovate-9895fb3.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-gateway-backend': patch
+---
+
+Updated dependency `eventsource` to `^4.0.0`.

plugins/gateway-backend/package.json

@@ -46,7 +46,7 @@
     "@backstage/backend-test-utils": "workspace:^",
     "@backstage/cli": "workspace:^",
     "@types/express": "^4.17.6",
-    "eventsource": "^3.0.6",
+    "eventsource": "^4.0.0",
     "wait-for-expect": "^3.0.2"
   }
 }

yarn.lock

@@ -5719,7 +5719,7 @@ __metadata:
     "@opentelemetry/api": "npm:^1.9.0"
     "@opentelemetry/core": "npm:^1.29.0"
     "@types/express": "npm:^4.17.6"
-    eventsource: "npm:^3.0.6"
+    eventsource: "npm:^4.0.0"
     express: "npm:^4.22.0"
     http-proxy-middleware: "npm:^3.0.3"
     wait-for-expect: "npm:^3.0.2"
@@ -30115,7 +30115,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"eventsource@npm:^3.0.2, eventsource@npm:^3.0.6":
+"eventsource@npm:^3.0.2":
   version: 3.0.7
   resolution: "eventsource@npm:3.0.7"
   dependencies:
@@ -30124,6 +30124,15 @@ __metadata:
   languageName: node
   linkType: hard
 
+"eventsource@npm:^4.0.0":
+  version: 4.1.0
+  resolution: "eventsource@npm:4.1.0"
+  dependencies:
+    eventsource-parser: "npm:^3.0.1"
+  checksum: 10/d23b1c2a56a1dd7344a151ca57d70ebc624972150395c1c82110bda1d2918487260e8ec76c1c79677406184ecb1847509a675d4ee5367925ef77f03c9cae594d
+  languageName: node
+  linkType: hard
+
 "evp_bytestokey@npm:^1.0.0, evp_bytestokey@npm:^1.0.3":
   version: 1.0.3
   resolution: "evp_bytestokey@npm:1.0.3"