docs: tweak SPEC/BOOTSTRAP.md

Co-Authored-By: Hugo Dias <hugomrdias@gmail.com>

Author: Alan Shaw

SPEC/BOOTSTRAP.md

@@ -4,7 +4,7 @@
   the addresses of the bootstrap nodes. These are the trusted peers from
   which to learn about other peers in the network.
 
-> Only edit this list if you understand the risks of adding or removing nodes
+> Only edit this list if you understand the risks of adding or removing nodes.
 
 * [bootstrap.add](#bootstrapadd)
 * [bootstrap.list](#bootstraplist)