bump memory limit in gnt-dal cluster (team#40972)

also retroactively update the limit in gnt-chi to reflect the actual
value there.

howto/ganeti.md

@@ -2749,7 +2749,7 @@ The upper limit for CPU count and memory size were doubled, to 16 and
 ```
 gnt-cluster modify --ipolicy-bounds-specs \
 max:cpu-count=16,disk-count=16,disk-size=1048576,\
-memory-size=65536,nic-count=8,spindle-use=12\
+memory-size=307200,nic-count=8,spindle-use=12\
 /min:cpu-count=1,disk-count=1,disk-size=1024,\
 memory-size=128,nic-count=1,spindle-use=1
 ```
@@ -2963,8 +2963,8 @@ The upper limit for CPU count and memory size were doubled, to 16 and
 
 ```
 gnt-cluster modify --ipolicy-bounds-specs \
-max:cpu-count=16,disk-count=16,disk-size=1048576,\
-memory-size=65536,nic-count=8,spindle-use=12\
+max:cpu-count=32,disk-count=16,disk-size=1048576,\
+memory-size=307200,nic-count=8,spindle-use=12\
 /min:cpu-count=1,disk-count=1,disk-size=1024,\
 memory-size=128,nic-count=1,spindle-use=1
 ```