Do not fetch Qt from Debian experimental when building for Qt6

Qt version in Debian Trixie is 6.6 as of September 2024. Therefore there
is no need to use experimental repositories.

README.md

@@ -348,12 +348,11 @@ sudo pacman -S qt6-base \
 ```
 
 #### Debian 13 [Testing/Sid] (Nheko QT6 Version)
-*As of February 2024, Nheko from git master requires QT 6.5 whereas Trixie has 6.4.2, so you must enable Debian's [Experimental Repository](https://wiki.debian.org/DebianExperimental) to install newer QT6.  This may not be necessary in the future and the `-t experimental` can be removed for the second set of build requirements.*  
 
 ```bash
 # Install build requirements
 sudo apt install -y cmake asciidoc-base libevent-dev libspdlog-dev libre2-dev liblmdb++-dev libcurl4-openssl-dev libssl-dev libolm-dev libcmark-dev nlohmann-json3-dev libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev libgstreamer-plugins-bad1.0-dev libkdsingleapplication-qt6-dev
-sudo apt install -y -t experimental qt6-base-dev qt6-tools-dev qt6-svg-dev qt6-multimedia-dev qt6-declarative-dev qtkeychain-qt6-dev qt6-base-private-dev qt6-declarative-private-dev
+sudo apt install -y qt6-base-dev qt6-tools-dev qt6-svg-dev qt6-multimedia-dev qt6-declarative-dev qtkeychain-qt6-dev qt6-base-private-dev qt6-declarative-private-dev
 # Clone nheko repository from github
 sudo apt install -y git
 git clone https://github.com/Nheko-Reborn/nheko && cd nheko