Fix profile render when the README.md size is larger than 1024 bytes (#25131)

Fixes https://github.com/go-gitea/gitea/issues/25094

`GetBlobContent` will only get the first 1024 bytes, if the README.md
size is larger than 1024 bytes,
We can not render the rest of them.
After this fix, we should provide the limited size to read when call
`GetBlobContent`.

After:

![image](22a42936-4cf8-40b4-a5c7-e384082beb0d)

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

tests/integration/api_packages_cargo_test.go

@@ -88,7 +88,7 @@ func testPackageCargo(t *testing.T, _ *neturl.URL) {
 		blob, err := commit.GetBlobByPath(path)
 		assert.NoError(t, err)
 
-		content, err := blob.GetBlobContent()
+		content, err := blob.GetBlobContent(1024)
 		assert.NoError(t, err)
 
 		return content