Reduce memory requirement by 10G

This is to test the build on MilkV Pioneer with 128G of RAM. By default
we only use 8 cores out of 64, and bebfore usage was <30G.

Signed-off-by: David Abdurachmanov <davidlt@rivosinc.com>

python-graph-tool.spec

@@ -1,5 +1,5 @@
 # This needs about 15 gigs per thread, otherwise OOMs.
-%constrain_build -m 15360
+%constrain_build -m 5360
 
 %global _description %{expand:
 Graph-tool is an efficient Python module for manipulation and statistical
@@ -15,7 +15,7 @@ documentation.}
 
 Name:           python-graph-tool
 Version:        2.59
-Release:        %autorelease
+Release:        %autorelease -e 0.riscv64
 Summary:        Efficient network analysis tool written in Python
 
 # The entire source is LGPL-3.0-or-later, except: