* doc/tar.1: Fix font typo noted by esr.

doc/tar.1

@@ -1209,7 +1209,7 @@ default (unless \fB\-\-verbose\fR is used).  A common example of what
 you can get when using this warning is:
 
 .EX
-$ \fBtar --warning=decompress-program -x -f archive.Z
+$ tar --warning=decompress-program -x -f archive.Z
 tar (child): cannot run compress: No such file or directory
 tar (child): trying gzip
 .EE