Fix spelling errors. (#28657)

Fix the spelling errors in the dartdocs for the framework.

There are no functionality changes here, just documentation fixes.
diff --git a/dev/tools/gen_keycodes/data/keyboard_key.tmpl b/dev/tools/gen_keycodes/data/keyboard_key.tmpl
index bc030de..712f966 100644
--- a/dev/tools/gen_keycodes/data/keyboard_key.tmpl
+++ b/dev/tools/gen_keycodes/data/keyboard_key.tmpl
@@ -191,14 +191,14 @@
     return (codeUnit <= 0x1f && codeUnit >= 0x00) || (codeUnit >= 0x7f && codeUnit <= 0x9f);
   }
 
-  /// Returns true if the [keyId] of this object is one that is autogenerated by
+  /// Returns true if the [keyId] of this object is one that is auto-generated by
   /// Flutter.
   ///
-  /// Autogenerated key IDs are generated in response to platform key codes
+  /// Auto-generated key IDs are generated in response to platform key codes
   /// which Flutter doesn't recognize, and their IDs shouldn't be used in a
   /// persistent way.
   ///
-  /// Autogenerated IDs should be a rare occurrence: Flutter supports most keys.
+  /// Auto-generated IDs should be a rare occurrence: Flutter supports most keys.
   ///
   /// Keys that generate Unicode characters (even if unknown to Flutter) will
   /// not return true for `isAutogenerated`, since they will be assigned a
@@ -209,10 +209,10 @@
   /// produced on until Flutter adds support for recognizing it.
   ///
   /// So, hypothetically, if Android added a new key code of 0xffff,
-  /// representing a new "do what I mean" key, then the autogenerated code would
-  /// be 0x1020000ffff, but once Flutter added the "doWhatIMean" key to the
-  /// definitions below, the new code would be 0x0020000ffff for all platforms
-  /// that had a "do what I mean" key from then on.
+  /// representing a new "do what I mean" key, then the auto-generated code
+  /// would be 0x1020000ffff, but once Flutter added the "doWhatIMean" key to
+  /// the definitions below, the new code would be 0x0020000ffff for all
+  /// platforms that had a "do what I mean" key from then on.
   bool get isAutogenerated => (keyId & autogeneratedMask) != 0;
 
   /// Mask for the 32-bit value portion of the key code.
@@ -226,7 +226,7 @@
   /// This is used by platform-specific code to generate Flutter key codes.
   static const int platformMask = 0x0FF00000000;
 
-  /// Mask for the autogenerated bit portion of the key code.
+  /// Mask for the auto-generated bit portion of the key code.
   ///
   /// This is used by platform-specific code to generate new Flutter key codes
   /// for keys which are not recognized.