Spread with concatenated group - Error: Each row of output must be identified by a unique combination of keys

I want to subsidize the data set to just one row by spreading a key field over concatenated values but I keep running into an error using the tidyr::spread() function. Here is a sample of my data set along with the concatenation:

dta <- data.frame(id = c("A001","A001","A001","A001","A001"),
           name = c("one", "one","one","one","one"),
           group=c("a","b","b","c","c"),
           category=c("I","N","N","N","N"), stringsAsFactors=F) 


dta %>% 
 group_by(category) %>% 
  mutate(gps = paste0(unique(group), collapse = "; "))


  id    name  group category gps  
  <chr> <chr> <chr> <chr>    <chr>
1 A001  one   a     I        a    
2 A001  one   b     N        b; c 
3 A001  one   b     N        b; c 
4 A001  one   c     N        b; c 
5 A001  one   c     N        b; c 


dta %>% 
 group_by(category) %>% 
  mutate(gps = paste0(unique(group), collapse = "; ")) %>% 
  tidyr::spread(category, gps)

Error: Each row of output must be identified by a unique combination of keys.
Keys are shared for 4 rows:
* 2, 3
* 4, 5

I want to achieve:

id    name    I      N 
<chr> <chr>  <chr> <chr> 
1 A001  on    a     b; c

Is this possible using the spread function? I tried to use the pivot_wider function but it also resulted in an error. I am just curious if I am missing something to boil the data down to 1 row.

Thanks!