Please fix the pragma in Keyboard.m to remove warnings while building for iOS

Hi! 👋

Firstly, thanks for your work on this project! 🙂

Today I used [patch-package](https://github.com/ds300/patch-package) to patch `@capacitor/keyboard@6.0.3` for the project I'm working on.

While building the project in Xcode I was getting a warning regarding the properties of KeyboardPlugin.

Here is the diff that solved my problem:

```diff
diff --git a/node_modules/@capacitor/keyboard/ios/Sources/KeyboardPlugin/Keyboard.m b/node_modules/@capacitor/keyboard/ios/Sources/KeyboardPlugin/Keyboard.m
index 29c0708..69cb4d1 100644
--- a/node_modules/@capacitor/keyboard/ios/Sources/KeyboardPlugin/Keyboard.m
+++ b/node_modules/@capacitor/keyboard/ios/Sources/KeyboardPlugin/Keyboard.m
@@ -43,7 +43,7 @@ @interface KeyboardPlugin ()
@end

#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wprotocol"
+#pragma clang diagnostic ignored "-Wobjc-protocol-property-synthesis"
// suppressing warnings of the type: "Class 'KeyboardPlugin' does not conform to protocol 'CAPBridgedPlugin'"
// protocol conformance for this class is implemented by a macro and clang isn't detecting that
@implementation KeyboardPlugin
```

This issue body was [partially generated by patch-package](https://github.com/ds300/patch-package/issues/296).

Open ios/Sources/KeyboardPlugin/Keyboard.m and inspect the diagnostic pragma around the KeyboardPlugin implementation. Build the iOS package in Xcode to reproduce the warning, then verify that the warning is gone and the existing KeyboardPlugin behavior remains unchanged.

Written by the indexing model from the issue text.