gnu: Remove references to meson-0.55.

This is a follow-up to 1eca979fb8da842e73c42f4f53be29b169810f2.

* gnu/packages/datastructures.scm, gnu/packages/fontutils.scm,
gnu/packages/terminals.scm: Don't import (gnu packages build-tools).
* gnu/packages/wm.scm: Remove comment.
* gnu/packages/emulators.scm (dosbox-staging)[arguments]: Remove meson
field.
* gnu/packages/package-management.scm (conan)[native-inputs]: Use meson.

gnu/packages/datastructures.scm

@@ -25,7 +25,6 @@
   #:use-module (gnu packages)
   #:use-module (gnu packages autotools)
   #:use-module (gnu packages boost)
-  #:use-module (gnu packages build-tools)   ;for meson-0.55
   #:use-module (gnu packages perl)
   #:use-module ((guix licenses) #:prefix license:)
   #:use-module (guix packages)

gnu/packages/emulators.scm

@@ -415,7 +415,7 @@ older games.")
         (base32 "07jwmmm1bhfxavlhl854cj8l5iy5hqx5hpwkkjbcwqg7yh9jfs2x"))))
     (build-system meson-build-system)
     (arguments
-     `(#:meson ,meson-0.55 #:configure-flags
+     `(#:configure-flags
        ;; These both try to git clone subprojects.
        (list "-Dunit_tests=disabled"     ; gtest
              "-Duse_mt32emu=false")))    ; mt32emu

gnu/packages/fontutils.scm

@@ -35,7 +35,6 @@
   #:use-module (gnu packages)
   #:use-module (gnu packages autotools)
   #:use-module (gnu packages bison)
-  #:use-module (gnu packages build-tools)   ;for meson-0.55
   #:use-module (gnu packages check)
   #:use-module (gnu packages compression)
   #:use-module (gnu packages datastructures)

gnu/packages/package-management.scm

@@ -1173,7 +1173,7 @@ written entirely in Python.")
        ("automake" ,automake)
        ("cmake" ,cmake)                 ;requires cmake >= 3.17
        ("git" ,git-minimal)
-       ("meson" ,meson-0.55)
+       ("meson" ,meson)
        ("ninja",ninja)
        ("pkg-config" ,pkg-config)
        ("python-bottle" ,python-bottle)

gnu/packages/terminals.scm

@@ -59,7 +59,6 @@
   #:use-module (guix utils)
   #:use-module (gnu packages)
   #:use-module (gnu packages autotools)
-  #:use-module (gnu packages build-tools)   ;for meson-0.55
   #:use-module (gnu packages check)
   #:use-module (gnu packages cmake)
   #:use-module (gnu packages compression)

gnu/packages/wm.scm

@@ -81,7 +81,7 @@
   #:use-module (gnu packages autotools)
   #:use-module (gnu packages base)
   #:use-module (gnu packages bison)
-  #:use-module (gnu packages build-tools) ;for meson-0.55
+  #:use-module (gnu packages build-tools)
   #:use-module (gnu packages calendar)
   #:use-module (gnu packages datastructures)
   #:use-module (gnu packages docbook)