[vim] remove vim expandtab comments on most of the files

app/tests/clock_tests.c

@@ -114,5 +114,3 @@ void clock_tests(void)
         printf("%u cycles per second\n", cycles);
     }
 }
-
-// vim: set noexpandtab:

app/tests/fibo.c

@@ -91,6 +91,3 @@ int fibo(int argc, const cmd_args *argv)
 
     return NO_ERROR;
 }
-
-// vim: set noexpandtab:
-

app/tests/thread_tests.c

@@ -662,5 +662,3 @@ int spinner(int argc, const cmd_args *argv)
 
     return 0;
 }
-
-/* vim: set ts=4 sw=4 noexpandtab: */

app/usbtest/descriptor.c

@@ -106,5 +106,3 @@ void usbtest_usb_setup(void)
     usbc_setup_endpoint(1, USB_OUT, 64);
     usbc_setup_endpoint(1, USB_IN, 64);
 }
-
-// vim: set ts=4 sw=4 expandtab: