bug#77000: grep.in.1: use the macro '.B' for one argument

[Bjarni Ingi Gislaosn]

--- grep.in.1   2025-03-13 20:55:51.123248073 +0000
+++ grep.in.1.new       2025-03-13 21:12:07.809760485 +0000
@@ -966,7 +966,7 @@ In basic regular expressions the meta-ch
 .BR | ,
 .BR ( ,
 and
-.BR )
+.B )
 lose their special meaning; instead use the backslashed
 versions
 .BR \e? ,