DAMD-133: fix a typo (DSGN_NAME → DSGN_NAM: Human-readable name for the design)

[michitaro]

The actual keyword for Human-readable name for the design of pfsDesign is DSGN_NAM instead of DSGN_NAME.

(It might be the implementation that should be fixed.)

[michitaro@obslog-ics pfsDesign]$ ls -l pfsDesign-0x66d10a1062719d1a.fits
-rw-rw-r--. 1 kiyoyabe naoj 417600 May 18 16:50 pfsDesign-0x66d10a1062719d1a.fits

[michitaro@obslog-ics pfsDesign]$ fold pfsDesign-0x66d10a1062719d1a.fits | head -36 | grep -i design
DSGN_NAM= '' / Name of design

[michitaro]

https://pfspipe.ipmu.jp/jira/browse/DAMD-133