Fix logo URLs
Looks like something went wrong with the preview in the last PR, this seems like it should work.
-![cocotb logo](/../../../../cocotb-web/blob/master/assets/img/cocotb-logo.svg#gh-light-mode-only)
-![cocotb logo](/../../../../cocotb-web/blob/master/assets/img/cocotb-logo-dark.svg#gh-dark-mode-only)
+![cocotb logo](/../../../../cocotb/cocotb-web/blob/master/assets/img/cocotb-logo.svg#gh-light-mode-only)
+![cocotb logo](/../../../../cocotb/cocotb-web/blob/master/assets/img/cocotb-logo-dark.svg#gh-dark-mode-only)
**cocotb** is a coroutine based cosimulation library for writing VHDL and Verilog testbenches in Python.
