[Hugo] Recommended packages exclude Python

hugo/content/installation/building/unix/third-party.md

@@ -53,12 +53,17 @@ Install required packages:
 ```
 $ sudo apt-get install build-essential git cmake \
   libgsl-dev libfftw3-dev libtiff5-dev \
-  python3 python3-dev python3-pip python3-numpy python3-matplotlib python3-lmfit \
   libboost-dev libboost-iostreams-dev \
   libboost-program-options-dev libboost-regex-dev \
   libcerf-dev qt6-base-dev qt6-svg-dev
 ```
 
+We assume that Python is [installed under pyenv]({{% relref "installation/py/linux" %}}));
+otherwise we also need the packages
+```
+  python3 python3-dev python3-pip python3-numpy python3-matplotlib python3-lmfit
+```
+
 Note: Normally we should also depend on `libcerf-dev`,
 which however is presently outdated.
 Therefore Debian users should install libcerf from source,
@@ -69,9 +74,14 @@ Install required packages:
 ```
 $ sudo zypper install gcc-c++ git-core cmake gsl-devel \
   libboost_*-devel fftw3-devel libcerf-devel libtiff-devel \
+  libqt6-qtbase-devel libqt6-qttools-devel libqt6-qtsvg-devel
+```
+
+We assume that Python is [installed under pyenv]({{% relref "installation/py/linux" %}}));
+otherwise we also need the packages
+```
   python3-devel python3-pip \
   python3-numpy-devel python3-matplotlib python3-lmfit \
-  libqt6-qtbase-devel libqt6-qttools-devel libqt6-qtsvg-devel
 ```
 
 ### MacOS