docs: minor improvement for docs (sablier-labs#1329)

Signed-off-by: ledigang <shuangcui@msn.com>

Author: ledigang

flow/src/SablierFlow.sol

@@ -466,7 +466,7 @@ contract SablierFlow is
 
     /// @inheritdoc ISablierFlow
     function setNativeToken(address newNativeToken) external override onlyComptroller {
-        // Check: provided token is not zero address.
+        // Check: provided token is not the zero address.
         if (newNativeToken == address(0)) {
             revert Errors.SablierFlow_NativeTokenZeroAddress();
         }
@@ -571,7 +571,7 @@ contract SablierFlow is
                          INTERNAL STATE-CHANGING FUNCTIONS
     //////////////////////////////////////////////////////////////////////////*/
 
-    /// @notice Overrides the {ERC-721._update} function to check that the stream is transferable.
+    /// @notice Overrides the {ERC721._update} function to check that the stream is transferable.
     ///
     /// @dev The transferable flag is ignored if the current owner is 0, as the update in this case is a mint and
     /// is allowed. Transfers to the zero address are not allowed, preventing accidental burns.

flow/src/interfaces/ISablierFlow.sol

@@ -441,7 +441,7 @@ interface ISablierFlow is
     ///
     /// Requirements:
     /// - `msg.sender` must be the comptroller contract.
-    /// - `newNativeToken` must not be zero address.
+    /// - `newNativeToken` must not be the zero address.
     /// - The native token must not be already set.
     /// @param newNativeToken The address of the native token.
     function setNativeToken(address newNativeToken) external;

lockup/src/SablierLockup.sol

@@ -529,7 +529,7 @@ contract SablierLockup is
         token.safeTransferFrom({ from: msg.sender, to: address(this), value: depositAmount });
     }
 
-    /// @notice Overrides the {ERC-721._update} function to check that the stream is transferable, and emits an
+    /// @notice Overrides the {ERC721._update} function to check that the stream is transferable, and emits an
     /// ERC-4906 event.
     /// @dev There are two cases when the transferable flag is ignored:
     /// - If the current owner is 0, then the update is a mint and is allowed.

lockup/src/interfaces/ISablierLockup.sol

@@ -173,7 +173,7 @@ interface ISablierLockup is
     /// @dev Emits a {Transfer}, {CancelLockupStream} and {MetadataUpdate} event.
     ///
     /// Notes:
-    /// - If there any tokens left for the recipient to withdraw, the stream is marked as canceled. Otherwise, the
+    /// - If there are any tokens left for the recipient to withdraw, the stream is marked as canceled. Otherwise, the
     /// stream is marked as depleted.
     /// - If the address is on the allowlist, this function will invoke a hook on the recipient.
     ///
@@ -234,11 +234,11 @@ interface ISablierLockup is
     /// @dev For more information, see the documentation for {nativeToken}.
     ///
     /// Notes:
-    /// - If `newNativeToken` is zero address, the function does not revert.
+    /// - If `newNativeToken` is the zero address, the function does not revert.
     ///
     /// Requirements:
     /// - `msg.sender` must be the comptroller contract.
-    /// - The current native token must be zero address.
+    /// - The current native token must be the zero address.
     /// @param newNativeToken The address of the native token.
     function setNativeToken(address newNativeToken) external;