refactor: updated String for better readability

Co-authored-by: Mattia Dal Ben <[email protected]>

kura/org.eclipse.kura.nm/src/main/java/org/eclipse/kura/nm/configuration/NMConfigurationServiceImpl.java

@@ -379,7 +379,7 @@ private Certificate getTrustedCertificateFromKeystore(String certificateName, Ke
             return cert.getCertificate();
         } else {
             throw new KuraException(KuraErrorCode.CONFIGURATION_ERROR,
-                    String.format("Certificate %s is not expected key type or not found.", certificateName));
+                    String.format("Certificate \"%s\" is not of the expected key type or not found.", certificateName));
         }
     }