Mark configure file as generated in .gitattributes

configure is regenerated from configure.ac using a custom container
with appropriate version of tools (quay.io/tiran/cpython_autoconf
by Christian Heimes).

As a result, configure falls into the same category as files generated
by Argument Clinic, Freeze and Parser/asdl_c.py. Due to size and churn
of these artifacts, they are marked in .gitattributes as generated so
GitHub Pull Request Diff Viewer collapses them into a short
notification. This commit does the same for configure.

Actually, configure diff is so large that sometimes it crosses
a threshold and GitHub collapses it by force with "Large diffs are not
rendered by default" or even "xxx additions, yyy deletions not shown
because the diff is too large. Please use a local Git client to view
these changes". See pythonGH-29756 as an extreme example and
<https://github.com/python/cpython/commits/main/configure> for
an average.

Author: arhadthedev

.gitattributes

@@ -60,6 +60,7 @@ Include/token.h             linguist-generated=true
 Lib/token.py                linguist-generated=true
 Parser/token.c              linguist-generated=true
 Programs/test_frozenmain.h  linguist-generated=true
+configure                   linguist-generated=true
 
 # Language aware diff headers
 # https://tekin.co.uk/2020/10/better-git-diff-output-for-ruby-python-elixir-and-more