Fixed typo in documentation (#2611)

Author: sanketsharma

docs/source/guide/executors.md

@@ -76,7 +76,7 @@ print("\nExecuted circuits:\n", *executor.executed_circuits, sep="\n")
 print("\nQuantum results:\n", *executor.quantum_results, sep="\n")
 ```
 
-To run a circuit of sequence of circuits, use the `Executor.evaluate` method.
+To run a circuit or sequence of circuits, use the `Executor.evaluate` method.
 
 ```{code-cell} ipython3
 import cirq

mitiq/executor/executor.py

@@ -118,7 +118,7 @@ def evaluate(
         quantum results are stored in ``self.quantum_results``.
 
         Args:
-            circuits: A single circuit of list of circuits.
+            circuits: A single circuit or list of circuits.
             observable: Observable O in the expression Tr[ρ O]. If None,
                 the ``executor`` must return a float (which corresponds to
                 Tr[ρ O] for a specific, fixed observable O).