Update conan install command in README (#3172)

Signed-off-by: Uilian Ries <uilianries@gmail.com>

README.md

@@ -30,7 +30,7 @@ see example [CMakeLists.txt](https://github.com/gabime/spdlog/blob/v1.x/example/
 * Arch Linux: `pacman -S spdlog`
 * openSUSE: `sudo zypper in spdlog-devel`
 * vcpkg: `vcpkg install spdlog`
-* conan: `spdlog/[>=1.4.1]`
+* conan: `conan install --requires=spdlog/[*]`
 * conda: `conda install -c conda-forge spdlog`
 * build2: ```depends: spdlog ^1.8.2```