Unreviewed, fix the internal tvOS build after 270746@main

Move the declaration of `-_internalAdjustSelectionWithOffset:lengthDelta:completionHandler` out of
the `HAVE(UI_WK_DOCUMENT_CONTEXT)` compile-time guard, so that it can be called on tvOS as well.
This method doesn't actually depend on `HAVE(UI_WK_DOCUMENT_CONTEXT)` at all, so it can be used in
the `HAVE(UI_ASYNC_TEXT_INTERACTION)` section. Note that this method doesn't actually depend on
`UIWKDocumentContext` at all.

* Source/WebKit/UIProcess/ios/WKContentViewInteraction.mm:
(-[WKContentView _internalAdjustSelectionWithOffset:lengthDelta:completionHandler:]):
(-[WKContentView adjustSelectionWithDelta:completionHandler:]):

Canonical link: https://commits.webkit.org/270790@main

Source/WebKit/UIProcess/ios/WKContentViewInteraction.mm

@@ -10037,13 +10037,6 @@ - (void)_removeContextMenuHintContainerIfPossible
     return webRequest;
 }
 
-- (void)_internalAdjustSelectionWithOffset:(NSInteger)offset lengthDelta:(NSInteger)lengthDelta completionHandler:(void (^)(void))completionHandler
-{
-    _page->updateSelectionWithDelta(offset, lengthDelta, [capturedCompletionHandler = makeBlockPtr(completionHandler)] {
-        capturedCompletionHandler();
-    });
-}
-
 - (void)adjustSelectionWithDelta:(NSRange)deltaRange completionHandler:(void (^)(void))completionHandler
 {
     RELEASE_ASSERT_ASYNC_TEXT_INTERACTIONS_DISABLED();
@@ -10073,7 +10066,14 @@ - (void)selectPositionAtPoint:(CGPoint)point withContextRequest:(UIWKDocumentReq
     }];
 }
 
-#endif
+#endif // HAVE(UI_WK_DOCUMENT_CONTEXT)
+
+- (void)_internalAdjustSelectionWithOffset:(NSInteger)offset lengthDelta:(NSInteger)lengthDelta completionHandler:(void (^)(void))completionHandler
+{
+    _page->updateSelectionWithDelta(offset, lengthDelta, [capturedCompletionHandler = makeBlockPtr(completionHandler)] {
+        capturedCompletionHandler();
+    });
+}
 
 - (void)insertTextPlaceholderWithSize:(CGSize)size completionHandler:(void (^)(UITextPlaceholder *))completionHandler
 {