Fix base64 output for linkedin icons and sed regex

[alexbraga]

The base64 outputs for both LinkedIn icons (dim and white) in the 'Removed Icons' section of the markdown.md file didn't match the correct values. Also, the regex for the sed command to add the SVG attribute fill="#ffffff" didn't include the necessary whitespace at the beginning of the replacement string. Another small fix was to add the 'global' flag to the regex, to handle logos with multiple paths, like the Java one.