test(input): change size tests to use stacked label placements (#29334)

Issue number: N/A

---------

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## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->

Some of the size screenshot tests use `label-placement="floating"`.
Because this label placement isn't scope we've gotten to yet, the
screenshots look broken. This is okay in itself, but it causes confusion
when the screenshots are updated for other unrelated features since
reviewers don't expect the appearance to be off.

## What is the new behavior?
<!-- Please describe the behavior or changes that are being added by
this PR. -->

Tests changed to use `label-placement="stacked"`, which is functionally
the same as `floating` when the input has a value, but has the proper
styling.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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## Other information

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screenshots of how the component looks before and after the change. -->

---------

Co-authored-by: ionitron <hi@ionicframework.com>

core/src/components/input/test/size/input.e2e.ts

@@ -22,13 +22,13 @@ configs({ modes: ['ionic-md'], directions: ['ltr'] }).forEach(({ title, screensh
         const input = page.locator('ion-input');
         await expect(input).toHaveScreenshot(screenshot(`input-size-large`));
       });
-      test('should render correctly with floating label', async ({ page }) => {
+      test('should render correctly with stacked label', async ({ page }) => {
         await page.setContent(
           `
           <ion-input
             size="large"
             label="Email"
-            label-placement="floating"
+            label-placement="stacked"
             value="hi@ionic.io"
           ></ion-input>
         `,
@@ -36,7 +36,7 @@ configs({ modes: ['ionic-md'], directions: ['ltr'] }).forEach(({ title, screensh
         );
 
         const input = page.locator('ion-input');
-        await expect(input).toHaveScreenshot(screenshot(`input-size-large-label-floating`));
+        await expect(input).toHaveScreenshot(screenshot(`input-size-large-label-stacked`));
       });
       test('should not have visual regressions with fill outline', async ({ page }) => {
         await page.setContent(
@@ -45,7 +45,7 @@ configs({ modes: ['ionic-md'], directions: ['ltr'] }).forEach(({ title, screensh
             fill="outline"
             size="large"
             label="Email"
-            label-placement="floating"
+            label-placement="stacked"
             value="hi@ionic.io"
           ></ion-input>
         `,
@@ -63,7 +63,7 @@ configs({ modes: ['ionic-md'], directions: ['ltr'] }).forEach(({ title, screensh
             shape="round"
             size="large"
             label="Email"
-            label-placement="floating"
+            label-placement="stacked"
             value="hi@ionic.io"
           ></ion-input>
         `,