docs: remove --recursive on git clone in quick start docs

[timadye]

Our first quick-start command

git clone --recursive https://github.com/acts-project/acts

doesn't work out of the box for many (most?) people, because --recursive checks out thirdparty/OpenDataDetector, which requires git-lfs, which isn't usually installed by default. It's on lxplus, but I didn't find it anywhere else by default.

I propose to remove the --recursive option in the quick-start docs. The ODD quick-start already explains git submodule, so there is no assumption that the user has already used git clone --recursive. Maybe this could also add a link to git lfs (I'll see about a small update).

An alternative would be to add git-lfs to the list of dependencies, but this could be misleading as it isn't a compile-time dependency.

[codecov]

Codecov Report

Merging #1539 (45b922b) into main (b99368a) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1539   +/-   ##
=======================================
  Coverage   48.47%   48.47%           
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  Files         381      381           
  Lines       20699    20699           
  Branches     9503     9503           
=======================================
  Hits        10034    10034           
  Misses       4112     4112           
  Partials     6553     6553           

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