Fix typos in the documentation. (#6359)

Author: smburdick

cirq-core/cirq/ops/pauli_gates.py

@@ -186,7 +186,7 @@ def basis(self) -> Dict[int, '_ZEigenState']:
 
     This is the `exponent=1` instance of the `cirq.XPowGate`.
 
-    The untary matrix of `cirq.X` is:
+    The unitary matrix of `cirq.X` is:
     $$
     \begin{bmatrix}
         0 & 1 \\

docs/start/intro.ipynb

@@ -162,9 +162,9 @@
     "\n",
     "- A `Circuit` is a collection of `Moment`s. \n",
     "- A `Moment` is a collection of `Operation`s that all act during the same abstract time slice. \n",
-    "- An `Operation` is a an effect that operates on a specific subset of Qubits. \n",
+    "- An `Operation` is an effect that operates on a specific subset of Qubits. \n",
     "  - The most common type of `Operation` is a `Gate` applied to several qubits (a \"`GateOperation`\"). \n",
-    "- The `Qubit`s of a circuit are implicitly defined by the operations - you can't allocate qubits to a Circuit\n",
+    "- The `Qubit`s of a circuit are implicitly defined by the operations - you can't allocate qubits to a Circuit.\n",
     "  "
    ]
   },