gitattributes: mark test21.ok binary, drop test42.in

This change does 2 things:
1) Mark src/testdir/test21.ok as binary by git.

After 0ed8ba3, test21.ok was treated by Git as a text file
using LF line endings. However, the test explicitly checks handling of
files with mixed line endings, so it must retain its literal LF and CR
endings and must not be modified by Git. Therefore, mark it explicitly
as binary.

2) Remove src/testdir/test42.in

This test was converted to the new-style test in v8.2.1316 and was
therefore deleted. There is no need to keep gitattributes rules for a
non-existing file.

related: #19086

Signed-off-by: Christian Brabandt <[email protected]>

Author: chrisbra

.gitattributes

@@ -1,12 +1,14 @@
-src/testdir/test42.in diff
-
 # The old test .ok files are expected to use LF line endings, even on Windows.
 # In src/testdir/Make_mvc.mak and src/testdir/Make_ming.mak, the test result
 # files .out are converted to LF line endings before being compared.
 # Therefore, if the .ok files' line endings are not specified and are
 # converted to CRLF, the comparison between .ok and .out will fail.
 src/testdir/test*.ok text eol=lf
 
+# This ok file contains literal CR LF endings. Should not be touched by git,
+# so handle as binary
+src/testdir/test21.ok -text
+
 # `vim.pot` is updated every time any of the *.c files are modified.  And as it
 # contains line numbers for strings from *.c files, inserting a line into a
 # single .c file may cause many lines in the `vim.pot` file to be updated.