Chore: address audit comments (#4)

* docs: fix natspec for `eta`, `done` and `planned`

* docs: fix typo on natspec for `done`

src/EmergencyDropSpell.sol

@@ -60,7 +60,7 @@ contract EmergencyDropSpell is EmergencySpellLike {
     address public immutable action;
     /// @notice The original spell action tag (i.e.: `extcodehash`).
     bytes32 public immutable tag;
-    /// @notice The original spell expiry time.
+    /// @notice The original spell earliest execution time.
     uint256 public immutable eta;
     /// @notice The original spell encoded call.
     bytes public sig;
@@ -76,7 +76,7 @@ contract EmergencyDropSpell is EmergencySpellLike {
      * @param _usr The original spell action address.
      * @param _tag The original spell action tag (i.e.: `extcodehash`).
      * @param _fax The original spell encoded call.
-     * @param _eta The original spell expiry time.
+     * @param _eta The original spell earliest execution time.
      */
     constructor(address _protego, address _usr, bytes32 _tag, bytes memory _fax, uint256 _eta) {
         protego = ProtegoLike(_protego);
@@ -109,12 +109,12 @@ contract EmergencyDropSpell is EmergencySpellLike {
         return string(abi.encodePacked("MakerDAO Drop Spell: ", protego.id(action, tag, sig, eta)));
     }
 
-    /// @notice Returns whether the original spell has been dropped or not.
+    /// @notice Returns true if the original spell has been dropped or has never been planned.
     function done() external view returns (bool) {
         return !planned();
     }
 
-    /// @notice Returns whether the original spell has been planned or not.
+    /// @notice Returns whether the original spell is currently planned or not.
     function planned() public view returns (bool) {
         return protego.planned(action, tag, sig, eta);
     }

src/Protego.sol

@@ -49,7 +49,7 @@ contract Protego {
      * @param _usr The address of the scheduled spell.
      * @param _tag The tag identifying the address.
      * @param _fax The encoded call to be made in `_usr`.
-     * @param _eta The expiry date.
+     * @param _eta The earliest execution time.
      * @return _spell The `EmergencyDropSpell` address.
      */
     function deploy(address _usr, bytes32 _tag, bytes memory _fax, uint256 _eta) public returns (address _spell) {
@@ -62,7 +62,7 @@ contract Protego {
      * @param _usr The address of the scheduled spell.
      * @param _tag The tag identifying the address.
      * @param _fax The encoded call to be made in `_usr`.
-     * @param _eta The expiry date.
+     * @param _eta The earliest execution time.
      */
     function id(address _usr, bytes32 _tag, bytes memory _fax, uint256 _eta) public pure returns (bytes32) {
         return keccak256(abi.encode(_usr, _tag, _fax, _eta));
@@ -73,7 +73,7 @@ contract Protego {
      * @param _usr The address of the scheduled spell.
      * @param _tag The tag identifying the address.
      * @param _fax The encoded call to be made in `_usr`.
-     * @param _eta The expiry date.
+     * @param _eta The earliest execution time.
      */
     function planned(address _usr, bytes32 _tag, bytes memory _fax, uint256 _eta) external view returns (bool) {
         return planned(id(_usr, _tag, _fax, _eta));

src/Protego.t.sol

@@ -77,7 +77,7 @@ contract ProtegoTest is DssTest {
         assertEq(protego.pause(), pause);
     }
 
-    function testDeploySpell() public {
+    function testDeployDropSpell() public {
         ConformingSpell badSpell = new ConformingSpell(pause, end);
 
         assertFalse(