Update circuit_testing.md

docs/src/specs/prover/circuit_testing.md

@@ -38,7 +38,7 @@ Now the constraint system is ready! We can start the main part of the test!
 ![Contest(8).png](<./img/circuit_testing/Contest(8).png>)
 
 Here we have hard coded a secret key with its associated public key, and generate a signature. We will test our circuit
-on these inputs! Next we “allocate” these inputs as witnessess:
+on these inputs! Next we “allocate” these inputs as witnesses:
 
 ![Contest(9).png](<./img/circuit_testing/Contest(9).png>)