Fix typos in API reference (#1177)

* Fix typos

* Match other ref cards

---------

Co-authored-by: Debbie Matthews <[email protected]>

Author: sfc-gh-jrieke

content/develop/api-reference/_index.md

@@ -1047,7 +1047,7 @@ edited = st.data_editor(df, num_rows="dynamic")
 
 <Image pure alt="screenshot" src="/images/api/file_uploader.jpg" />
 
-<h4>File Uploader</h4>
+<h4>File uploader</h4>
 
 Display a file uploader widget.
 
@@ -1436,7 +1436,7 @@ c.write("This will show second")
 
 <Image pure alt="screenshot" src="/images/api/dialog.jpg" />
 
-<h4>Modal dialogs</h4>
+<h4>Modal dialog</h4>
 
 Insert a modal dialog that can rerun independently from the rest of the script.
 
@@ -1945,7 +1945,7 @@ st.switch_page("pages/my_page.py")
 
 <Image pure alt="screenshot" src="/images/api/dialog.jpg" />
 
-<h4>Modal dialogs</h4>
+<h4>Modal dialog</h4>
 
 Insert a modal dialog that can rerun independently from the rest of the script.
 

content/develop/api-reference/control-flow/_index.md

@@ -15,7 +15,7 @@ By default, Streamlit apps execute the script entirely, but we allow some functi
 
 <Image pure alt="screenshot" src="/images/api/dialog.jpg" />
 
-<h4>Modal dialogs</h4>
+<h4>Modal dialog</h4>
 
 Insert a modal dialog that can rerun independently from the rest of the script.
 

content/develop/api-reference/layout/_index.md

@@ -45,7 +45,7 @@ c.write("This will show second")
 
 <Image pure alt="screenshot" src="/images/api/dialog.jpg" />
 
-<h4>Modal dialogs</h4>
+<h4>Modal dialog</h4>
 
 Insert a modal dialog that can rerun independently from the rest of the script.