Disable clang-format in Matlab files

Matlab files extension is the same as ObjC, which is .m
This makes clang-format think that those files are ObjC and then it
wrongly formats them, leading to output that doesn't compile at all.
It's a known issue and the solution is to disable it in Matlab files.

I don't want to disable ObjC in whole folders, because of 2 reasons:
1) I want ObjC to be properly formatted if new files are added in the
   future
2) C++ header files are interpreted as ObjC and it will disable their
   formatting

According to clang documentation
(https://clang.llvm.org/docs/ClangFormatStyleOptions.html#disabling-formatting-on-a-piece-of-code), we can disable formatting inline.
However, comments in Matlab are prefixed with `%` and not `//`, so I
thought of a kinda hacky solution, which is `% // clang-format off`, and
it works perfectly.

No-Iwyu: Includes didn't change and it isn't related to formatting
Bug: webrtc:42225392
Change-Id: I281462fd1aecd3ff0428e6ee974514ebabc696ec
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/374060
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#43700}

modules/audio_coding/neteq/test/delay_tool/parse_delay_file.m

@@ -1,3 +1,4 @@
+%  // clang-format off
 %
 %  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
 %

modules/audio_coding/neteq/test/delay_tool/plot_neteq_delay.m

@@ -1,3 +1,4 @@
+%  // clang-format off
 %
 %  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
 %

modules/audio_processing/test/apmtest.m

@@ -1,3 +1,4 @@
+%  // clang-format off
 %
 %  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
 %

tools_webrtc/matlab/maxUnwrap.m

@@ -1,3 +1,4 @@
+%  // clang-format off
 function sequence = maxUnwrap(sequence, max)
 %
 % sequence = maxUnwrap(sequence, max)

tools_webrtc/matlab/parseLog.m

@@ -1,3 +1,4 @@
+%  // clang-format off
 function parsed = parseLog(filename)
 %
 % parsed = parseLog(filename)

tools_webrtc/matlab/rtpAnalyze.m

@@ -1,3 +1,4 @@
+%  // clang-format off
 function rtpAnalyze( input_file )
 %RTP_ANALYZE Analyze RTP stream(s) from a txt file
 %   The function takes the output from the command line tool rtp_analyze