♻️💄 simplify KorAPConnection class instantiations to modern syntax

Update all class instantiations from `new("KorAPConnection")` to `KorAPConnection()`.
This is possible with R >= 4.0.

Change-Id: I01131fb32045e084cafbb9e05cd8ba99f8f20f1b
diff --git a/demo/frequenciesOverDomains.R b/demo/frequenciesOverDomains.R
index 6607893..8da5cc8 100755
--- a/demo/frequenciesOverDomains.R
+++ b/demo/frequenciesOverDomains.R
@@ -5,7 +5,7 @@
 library(RKorAPClient)
 library(ggplot2)
 
-freqPerDomain <- function(query, con = new("KorAPConnection", verbose = TRUE)) {
+freqPerDomain <- function(query, con = KorAPConnection(verbose = TRUE)) {
   g <- corpusQuery(con, query = query, vc="") %>%
     fetchAll() %>%
     slot("collectedMatches") %>%