Removing obsolete documentation

doc/compiling-geth-on-debian.md

-# Compiling geth on Debian
-
-## Prerequisites
-
-1. `mkdir ~/new ~/bin`
-2. `cd ~/new`
-3. `sudo apt install build-essential git libjson-perl`
-4. `git clone https://github.com/ethereum/go-ethereum`
-
-## Compiling Go itself (takes less than 5 minutes)
-
-Go is only needed for compiling geth - afterwards we can delete it
-
-1. Download __go*.linux-amd64.tar.gz__ from [https://golang.org/dl/] e.g. [https://dl.google.com/go/go1.11.linux-amd64.tar.gz]
-2. `tar -xzf go*.tar.gz`
-3. `export PATH=${HOME}/new/go/bin:${PATH}:${HOME}/bin`
-4. `cd go-ethereum`
-5. `make geth`
-6. `cp build/bin/geth ~/bin/`
-7. `cd ..`
-8. `rm -r ~/new/go`
-
-## Compililng Solc takes a while (like 20-50 times longer than compiling geth)
-
-If you wish to compile contracts too, compile Solidity as well.
-
-$ `git clone --recursive https://github.com/ethereum/solidity`
-$ `cd solidity`
-$ `git submodule update --init --recursive`
-$ `./scripts/install_deps.sh`
-$ `mkdir build`
-$ `cd build`
-$ `cmake .. && make`
-$ `cp -p solc/solc ~/bin/`

doc/installing-geth-on-ubuntu.md

-$ `su`
-# `apt install software-properties-common libjson-perl`
-# `add-apt-repository -y ppa:ethereum/ethereum`
-# `apt update`
-# `apt install ethereum`