Fix mutate_each() and summarise_each() deprecation warnings

[DavisVaughan]

Closes #6869

[moodymudskipper]

For static analysis purpose, and general exploration by printing functions, shouldn't the deprecation warnings be triggered directly by the exported functions ?

This doesn't look deprecated, after being suggested by autocomplete dplyr::summ :

dplyr::summarize_each
#> function (tbl, funs, ...) 
#> {
#>     summarise_each_impl(tbl, funs, enquos(...), "summarise_each")
#> }
#> <bytecode: 0x12a0b8208>
#> <environment: namespace:dplyr>

^{Created on 2023-10-06 with reprex v2.0.2}