[chore] removed deprecated options gce, gke from the resourcedetection processor readme (open-telemetry#30665)

**Description:** <Describe what has changed.>
Some time ago `gce` and `gke` detectors were
[deprecated](open-telemetry#10347)
to use a single `gcp` detector.
This PR updates README to remove mentions of `gce` and `gke` detectors

Author: mar4uk

processor/resourcedetectionprocessor/README.md

@@ -547,7 +547,7 @@ See: [TLS Configuration Settings](https://github.com/open-telemetry/opentelemetr
 ## Configuration
 
 ```yaml
-# a list of resource detectors to run, valid options are: "env", "system", "gce", "gke", "ec2", "ecs", "elastic_beanstalk", "eks", "lambda", "azure", "heroku", "openshift"
+# a list of resource detectors to run, valid options are: "env", "system", "gcp", "ec2", "ecs", "elastic_beanstalk", "eks", "lambda", "azure", "heroku", "openshift"
 detectors: [ <string> ]
 # determines if existing resource attributes should be overridden or preserved, defaults to true
 override: <bool>
@@ -604,11 +604,6 @@ resourcedetection:
 
 Note that if multiple detectors are inserting the same attribute name, the first detector to insert wins. For example if you had `detectors: [eks, ec2]` then `cloud.platform` will be `aws_eks` instead of `ec2`. The below ordering is recommended.
 
-### GCP
-
-* gke
-* gce
-
 ### AWS
 
 * lambda