Since 99d9cb0b0d6498d678de426a81e622dd3e3750d6 runs all tests with HOME set to a temporary directory, this code setting the cache directory to a temporary directory is no longer needed. `cache_dir()` will choose a directory in the home directory if neither KITTY_CACHE_DIRECTORY or XDG_CACHE_HOME are set.
Without this, kitty fails to compile:
```
glfw/cocoa_init.m:462:14: error: case value not in enumerated type
'NSEventModifierFlags' (aka 'enum NSEventModifierFlags')
[-Werror,-Wswitch]
case (NSEventModifierFlagShift | NSEventModifierFlagOption):
^
glfw/cocoa_init.m:465:14: error: case value not in enumerated type
'NSEventModifierFlags' (aka 'enum NSEventModifierFlags')
[-Werror,-Wswitch]
case (NSEventModifierFlagShift | NSEventModifierFlagCommand):
^
```
I thought about changing the type of the `modifierFlags` function parameter from `NSEventModifierFlags` to `NSUInteger` since `NSEventModifierFlags` is defined as an enum according to https://developer.apple.com/documentation/appkit/nseventmodifierflags?language=objc and is technically not the proper type for a bit field. But since Apple themselves define `modifierFlags` as `NSEventModifierFlags` according to https://developer.apple.com/documentation/appkit/nsevent/1534405-modifierflags?language=objc, I think the fix in this commit is better.
This warning was introduced with commit f9944e614088c4977ad9c9f1d1b44d97643e8d5b.
Slight performance improvement, maybe?
Also, `kitty/graphics.h` has been reverted to the original version;
this version would be better in that aspect too.
It uses draw_graphics, which uses a scissor, but the scissor was set by
the last call to draw_cells() which is not called during a resize,
leaving us with an incorrect scissor.
Fixes#4160
