How can I get rid of the back-tic inside this table generated by `kableExtra` in `xaringan` slides?

How can I get rid of the back-tic inside this table generated by kableExtra in xaringan slides?

library(knitr)
library(kableExtra)

text_tbl <- data.frame(
   a= c("1", "2","...","L",""),
   b= c("$O_{11}$","$O_{21}$","...","$O_{L1}$","$n_{.1}$"),
   c= c("$O_{11}$","$O_{22}$","...","$O_{L2}$","$n_{.2}$"),
   d= c("...","...","...","...","..."),
   e= c("$O_{C1}$","$O_{C2}$","...","$O_{LC}$","$n_{.C}$"),
   f= c("$n_{1.}$","$n_{2.}$","...","$n_{L.}$","$N$"))
kable(text_tbl, "html", booktabs = T, col.names = c("","1","2","...","C"," "), escape=F) %>%
  kable_styling(full_width = F,bootstrap_options = "striped") %>%
  add_header_above(c(" Variável A", "Variável B" = 4, " ")) %>%
  column_spec(1, bold = T) %>%
  column_spec(2)

I inspected the HTML code generated, and I didn't see any back-tics.

PS: I made the same question on Stack Overflow and on RStudio Community.

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yihui / xaringan

How can I get rid of the back-tic inside this table generated by `kableExtra` in `xaringan` slides? #264