A couple more grammar fixes

CREDITS

@@ -1,9 +1,8 @@
 # Copyright (C) 2015-2023: The University of Edinburgh, United Kingdom
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 #                 Authors: Craig Warren, Antonis Giannopoulos, and John Hartley
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+#
 # This is the official list of entities and people who have contributed to gprMax
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+#
 # Please keep the lists sorted alphabetically (by surname for individuals).
 
 gprMax has been supported through research projects funded by: