fix: typos in documentation files (#898)

* Update usage.md

* Update glossary.md

Author: leopardracer

apps/docs/versioned_docs/version-V1/usage.md

@@ -26,7 +26,7 @@ With the Client contract as the owner of the Semaphore contract, the Client
 contract may call owner-only Semaphore functions such as
 `addExternalNullifier()`.
 
-## Add, deactivate, or reactivate external nullifiiers
+## Add, deactivate, or reactivate external nullifiers
 
 These functions add, deactivate, and reactivate an external nullifier respectively.
 As each identity can only signal once to an external nullifier, and as a signal

apps/docs/versioned_docs/version-V3/glossary.md

@@ -37,7 +37,7 @@ For more information, see [Merkle tree in Wikipedia](https://en.wikipedia.org/wi
 
 ## Nullifier
 
-A value used to prevent double entry or double signalling.
+A value used to prevent double entry or double signaling.
 
 See [Circuit nullifier hash](/V3/technical-reference/circuits/#nullifier-hash).