Update index.bs

Co-authored-by: Jan-Ivar Bruaroey <jan-ivar@users.noreply.github.com>

Author: youennf

index.bs

@@ -363,7 +363,7 @@ The <dfn method for="SFrameEncrypterKeyManager">setEncryptionKey(|key|, |keyID|)
 1. If |keyID| is a {{bigint}} which cannot be represented as a integer between 0 and 2<sup>64</sup>-1 inclusive, [=reject=] |promise| with a {{RangeError}} exception and abort these steps.
 1.  Set |this|.`[[currentKeyId]]` to |keyId|.
 1. [=In parallel=], run the following steps:
-    1. Set |key| and |keyID| as key material to use for the SFrame transform encryption algorithm, as defined by [[RFC9605]].
+    1. Set the SFrame transform encryption algorithm's key material to |key| and |keyID|, as defined by [[RFC9605]].
     1. If setting the key material fails, [=queue a task=] to [=reject=] |promise| with an {{InvalidModificationError}} exception and abort these steps.
     1. [=Queue a task=] to [=resolve=] |promise| with undefined.
 1. Return |promise|.