Revert boxtree req back to main

Author: inducer

requirements.txt

@@ -10,7 +10,7 @@ git+https://github.com/inducer/pytools.git#egg=pytools
 git+https://github.com/inducer/pymbolic.git#egg=pymbolic
 git+https://github.com/inducer/islpy.git#egg=islpy
 git+https://github.com/inducer/pyopencl.git#egg=pyopencl
-git+https://github.com/alexfikl/boxtree.git@towards-array-context#egg=boxtree
+git+https://github.com/alexfikl/boxtree.git#egg=boxtree
 git+https://github.com/inducer/loopy.git#egg=loopy
 git+https://github.com/inducer/arraycontext.git#egg=arraycontext
 git+https://github.com/inducer/pyfmmlib.git#egg=pyfmmlib