cmd/clef: spelling correction (#19973)

cmd/clef/README.md

@@ -914,7 +914,7 @@ A UI should conform to the following rules.
   * For example, not load icons, stylesheets from the internet
   * Not load files from the filesystem, unless they reside in the same local directory (e.g. config files)
 * A Graphical UI MUST show the blocky-identicon for ethereum addresses.
-* A UI MUST warn display approproate warning if the destination-account is formatted with invalid checksum.
+* A UI MUST warn display appropriate warning if the destination-account is formatted with invalid checksum.
 * A UI MUST NOT open any ports or services
   * The signer opens the public port
 * A UI SHOULD verify the permissions on the signer binary, and refuse to execute or warn if permissions allow non-user write.