Actually install ngsPETSc using pip (#3873) #6089

Job	Run time
Build Firedrake (real, default)	1h 19m 27s
Set the Docker release tag	3s
Build Firedrake (complex, --complex, complex)	1h 17m 47s
Build Docker containers / docker_env / Build the firedrake-env container	39m 5s
Build Docker containers / docker_vanilla / Build the firedrake-vanilla container	30m 53s
Build Docker containers / docker_complex / Build the firedrake-complex container	32m 21s
Build Docker containers / docker_docdeps / Build the firedrake-docdeps container	6h 0m 3s
Build Docker containers / docker_firedrake / Build the firedrake container	9m 26s
Build Docker containers / docker_jupyter / Build the firedrake-jupyter container	4m 50s
	10h 33m 55s

Provide feedback