chore(inputs): Remove unnecessary nil check (#13749)

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

plugins/inputs/prometheus/prometheus.go

@@ -410,10 +410,8 @@ func (p *Prometheus) gatherURL(u URLAndAddress, acc telegraf.Accumulator) error
 		req.SetBasicAuth(p.Username, p.Password)
 	}
 
-	if p.HTTPHeaders != nil {
-		for key, value := range p.HTTPHeaders {
-			req.Header.Set(key, value)
-		}
+	for key, value := range p.HTTPHeaders {
+		req.Header.Set(key, value)
 	}
 
 	var resp *http.Response

plugins/inputs/vsphere/endpoint.go

@@ -1388,11 +1388,9 @@ func (e *Endpoint) populateTags(objectRef *objectRef, resourceType string, resou
 	}
 
 	// Fill in custom values if they exist
-	if objectRef.customValues != nil {
-		for k, v := range objectRef.customValues {
-			if v != "" {
-				t[k] = v
-			}
+	for k, v := range objectRef.customValues {
+		if v != "" {
+			t[k] = v
 		}
 	}
 }