Remove exact version constraint from dub failing-meson tests

These are always failing just because the exact version constraint isn't
satisfied, e.g. "ERROR: Meson version is 0.53.999 but project requires
0.48.0"

test cases/failing/86 dub libray/meson.build

@@ -1,3 +1,3 @@
-project('dub', 'd', meson_version: '0.48.0')
+project('dub', 'd')
 
 dependency('dubtestproject', method: 'dub') # Not library (none)

test cases/failing/87 dub executable/meson.build

@@ -1,3 +1,3 @@
-project('dub', 'd', meson_version: '0.48.0')
+project('dub', 'd')
 
 dependency('dubtestproject:test1', method: 'dub') # Not library (executable)

test cases/failing/88 dub compiler/meson.build

@@ -1,4 +1,4 @@
-project('dub', 'd', meson_version: '0.48.0')
+project('dub', 'd')
 
 if meson.get_compiler('d').get_id() == 'dmd'
   if host_machine.system() == 'windows' or host_machine.system() == 'cygwin'