Bug 32475: Replace "System prefs" with "System preferences" on log viewer tool

Bug 32475: Replace "System prefs" with "System preferences" on log viewer tool

Basically, the phrase "System prefs" used on the log viewer page (viewlog.pl) is slang and we should use the correct terminology that we use everywhere else.

Test Plan:
1) Apply this patch
2) Browes to Tools > Log viewer
3) Note under Modules, is shows "System preferences" now instead of
   "System prefs"

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>