curl.1: remove URL encoding phrase from --data description

... it could be misleading a reader into thinking it _has_ to be encoded.

docs/curl.1

@@ -287,11 +287,11 @@ data pieces specified will be merged together with a separating
 chunk that looks like \&'name=daniel&skill=lousy'.
 
 If you start the data with the letter @, the rest should be a file name to
-read the data from, or - if you want curl to read the data from stdin.  The
-contents of the file must already be URL-encoded. Multiple files can also be
-specified. Posting data from a file named 'foobar' would thus be done with
-\fI--data\fP @foobar. When --data is told to read from a file like that,
-carriage returns and newlines will be stripped out.
+read the data from, or - if you want curl to read the data from
+stdin. Multiple files can also be specified. Posting data from a file
+named 'foobar' would thus be done with \fI--data\fP @foobar. When --data is
+told to read from a file like that, carriage returns and newlines will be
+stripped out.
 .IP "-D, --dump-header <file>"
 Write the protocol headers to the specified file.