gnu: Remove trademark acknowledgements.

* gnu/packages/imagemagick.scm (imagemagick), gnu/packages/python.scm
(python-xlrd), gnu/packages/wordnet.scm (wordnet) [description]:
Remove trademark acknowledgements.

gnu/packages/imagemagick.scm

@@ -100,7 +100,7 @@
     (home-page "http://www.imagemagick.org/")
     (synopsis "Create, edit, compose, or convert bitmap images")
     (description
-     "ImageMagick® is a software suite to create, edit, compose, or convert
+     "ImageMagick is a software suite to create, edit, compose, or convert
 bitmap images.  It can read and write images in a variety of formats (over 100)
 including DPX, EXR, GIF, JPEG, JPEG-2000, PDF, PhotoCD, PNG, Postscript, SVG,
 and TIFF.  Use ImageMagick to resize, flip, mirror, rotate, distort, shear and

gnu/packages/python.scm

@@ -5732,7 +5732,7 @@ object to help create WSGI responses.")
     (home-page "http://www.python-excel.org/")
     (synopsis "Library for extracting data from Excel files")
     (description "This packages provides a library to extract data from
-spreadsheets using Microsoft Excel® proprietary file formats @samp{.xls} and
+spreadsheets using Microsoft Excel proprietary file formats @samp{.xls} and
 @samp{.xlsx} (versions 2.0 onwards).  It has support for Excel dates and is
 Unicode-aware.  It is not intended as an end-user tool.")
     (license bsd-3)))

gnu/packages/wordnet.scm

@@ -83,7 +83,7 @@
     (home-page "http://wordnet.princeton.edu/")
     (synopsis "Lexical database for the English language")
     (description
-     "WordNet® is a large lexical database of English.  Nouns, verbs,
+     "WordNet is a large lexical database of English.  Nouns, verbs,
 adjectives and adverbs are grouped into sets of cognitive synonyms (synsets),
 each expressing a distinct concept.  Synsets are interlinked by means of
 conceptual-semantic and lexical relations.  The resulting network of