docs: update client.files.upload usage in README (use the correct par…

…ameter name)

README.md

@@ -87,7 +87,7 @@ download the file in console.
 python code.
 
 ```python
-file = client.files.upload(path='a11.txt')
+file = client.files.upload(file='a11.txt')
 response = client.models.generate_content(
     model='gemini-2.0-flash-001',
     contents=['Could you summarize this file?', file]
@@ -751,8 +751,8 @@ Files are only supported in Gemini Developer API.
 ### Upload
 
 ```python
-file1 = client.files.upload(path='2312.11805v3.pdf')
-file2 = client.files.upload(path='2403.05530.pdf')
+file1 = client.files.upload(file='2312.11805v3.pdf')
+file2 = client.files.upload(file='2403.05530.pdf')
 
 print(file1)
 print(file2)
@@ -761,7 +761,7 @@ print(file2)
 ### Delete
 
 ```python
-file3 = client.files.upload(path='2312.11805v3.pdf')
+file3 = client.files.upload(file='2312.11805v3.pdf')
 
 client.files.delete(name=file3.name)
 ```