docs: small fixes (#26154)

src/nvim/eval/funcs.c

@@ -7440,7 +7440,7 @@ static void f_setenv(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   char valbuf[NUMBUFLEN];
   const char *name = tv_get_string_buf(&argvars[0], namebuf);
 
-  // seting an environment variable may be dangerous, e.g. you could
+  // setting an environment variable may be dangerous, e.g. you could
   // setenv GCONV_PATH=/tmp and then have iconv() unexpectedly call
   // a shell command using some shared library:
   if (check_secure()) {