Remove Base64'ing of file contents

Updated example of reading secret values from a file so that it doesn't base64 the contents in the file before `kubectl` reads it.

Author: walker-tom

content/en/docs/tasks/configmap-secret/managing-secret-using-kubectl.md

@@ -42,11 +42,11 @@ characters.
 
 ### Use source files
 
-1.  Store the credentials in files with the values encoded in base64:
+1.  Store the credentials in files:
 
     ```shell
-    echo -n 'admin' | base64 > ./username.txt
-    echo -n 'S!B\*d$zDsb=' | base64 > ./password.txt
+    echo -n 'admin' > ./username.txt
+    echo -n 'S!B\*d$zDsb=' > ./password.txt
     ```
     The `-n` flag ensures that the generated files do not have an extra newline
     character at the end of the text. This is important because when `kubectl`
@@ -199,4 +199,4 @@ kubectl delete secret db-user-pass
 
 - Read more about the [Secret concept](/docs/concepts/configuration/secret/)
 - Learn how to [manage Secrets using config file](/docs/tasks/configmap-secret/managing-secret-using-config-file/)
-- Learn how to [manage Secrets using kustomize](/docs/tasks/configmap-secret/managing-secret-using-kustomize/)
+- Learn how to [manage Secrets using kustomize](/docs/tasks/configmap-secret/managing-secret-using-kustomize/)