smurf: pol2map: Remove non-ASCII characters

The non-ASCII micro characters that were in there cause python to fall
over on some systems:

File "/net/rogue1/work/jkaroly/star_CentOS6/star-nightly/bin/smurf/pol2map.py", line 525
SyntaxError: Non-ASCII character '\xce' in file /net/rogue1/work/jkaroly/star_CentOS6/star-nightly/bin/smurf/pol2map.py on line 526,
but no encoding declared;
see http://python.org/dev/peps/pep-0263/ for details

(cherry picked from commit f3fa33e)

applications/smurf/scripts/pol2map.py

@@ -522,7 +522,7 @@
 *        (approximately) 13 arc-seconds (the 850 um beam width), and
 *        also reduces the noise. The smoothing kernel is derived from the
 *        two-component beam models described in the paper "A Decade of
-*        SCUBA-2: A Comprehensive Guide to Calibrating 450 μm and 850 μm
+*        SCUBA-2: A Comprehensive Guide to Calibrating 450 um and 850 um
 *        Continuum Data at the JCMT" (Mairs et al, 2021). If parameter
 *        MAPVAR is TRUE, the individual observation maps will be smoothed
 *        prior to determining the variances, thus ensuring that the