[instrumentation] Remove env var prefix validation (open-telemetry#2768)

* Remove env var prefix validation

* changelog

Author: TylerHelmuth

.chloggen/remove-env-var-validation.yaml

@@ -0,0 +1,16 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. collector, target allocator, auto-instrumentation, opamp, github action)
+component: instrumentation
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Remove env var prefix validation
+
+# One or more tracking issues related to the change
+issues: [2768]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:

apis/v1alpha1/instrumentation_webhook.go

@@ -31,11 +31,6 @@ import (
 	"github.com/open-telemetry/opentelemetry-operator/pkg/constants"
 )
 
-const (
-	envPrefix       = "OTEL_"
-	envSplunkPrefix = "SPLUNK_"
-)
-
 var (
 	_                                  admission.CustomValidator = &InstrumentationWebhook{}
 	_                                  admission.CustomDefaulter = &InstrumentationWebhook{}
@@ -245,44 +240,9 @@ func (w InstrumentationWebhook) validate(r *Instrumentation) (admission.Warnings
 	default:
 		return warnings, fmt.Errorf("spec.sampler.type is not valid: %s", r.Spec.Sampler.Type)
 	}
-
-	// validate env vars
-	if err := w.validateEnv(r.Spec.Env); err != nil {
-		return warnings, err
-	}
-	if err := w.validateEnv(r.Spec.Java.Env); err != nil {
-		return warnings, err
-	}
-	if err := w.validateEnv(r.Spec.NodeJS.Env); err != nil {
-		return warnings, err
-	}
-	if err := w.validateEnv(r.Spec.Python.Env); err != nil {
-		return warnings, err
-	}
-	if err := w.validateEnv(r.Spec.DotNet.Env); err != nil {
-		return warnings, err
-	}
-	if err := w.validateEnv(r.Spec.Go.Env); err != nil {
-		return warnings, err
-	}
-	if err := w.validateEnv(r.Spec.ApacheHttpd.Env); err != nil {
-		return warnings, err
-	}
-	if err := w.validateEnv(r.Spec.Nginx.Env); err != nil {
-		return warnings, err
-	}
 	return warnings, nil
 }
 
-func (w InstrumentationWebhook) validateEnv(envs []corev1.EnvVar) error {
-	for _, env := range envs {
-		if !strings.HasPrefix(env.Name, envPrefix) && !strings.HasPrefix(env.Name, envSplunkPrefix) {
-			return fmt.Errorf("env name should start with \"OTEL_\" or \"SPLUNK_\": %s", env.Name)
-		}
-	}
-	return nil
-}
-
 func validateJaegerRemoteSamplerArgument(argument string) error {
 	parts := strings.Split(argument, ",")