replace debian/compat with debhelper-compat

While building the package, by using equivs-build and debian/control
file, I got the following error:

```
root@a625b7a1de7c:/mpv-build# equivs-build --full debian/control
dpkg-buildpackage: info: source package mpv
dpkg-buildpackage: info: source version 1.0
dpkg-buildpackage: info: source distribution unstable
dpkg-buildpackage: info: source changed by Kevin Mitchell <[email protected]>
dpkg-buildpackage: info: host architecture amd64
 dpkg-source --before-build .
 debian/rules clean
dh clean
dh: error: Please specify the compatibility level in debian/compat or via Build-Depends: debhelper-compat (= X)
make: *** [debian/rules:3: clean] Error 255
dpkg-buildpackage: error: debian/rules clean subprocess returned exit status 2
Error in the build process: exit status 2
```
Based on the error message, I replaced debian/compat with
debhelper-compate (= 12) in debian/control file. The existing
compat file didn't help to build the package.

[Reference](FooBarWidget/debian-packaging-for-the-modern-developer#8 (comment))

Changes to be committed:
      deleted:    compat
      modified:   control

Author: ilkermeliksitki

debian/compat

@@ -8,6 +8,7 @@ Build-Depends:
  automake,
  c-compiler | gcc,
  debhelper (>= 12),
+ debhelper-compat (= 12),
  glslang-dev,
  ladspa-sdk,
  libasound2-dev [linux-any],