meson: adjust nlohmann-json dependency

Simplify the meson directive for nlohmann-json dependency and rename the
wrap file to align with other repositories.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I6ad9d4fe3e8fa24673b736bab81e2fcabc51f1a0
diff --git a/subprojects/nlohmann_json.wrap b/subprojects/nlohmann_json.wrap
new file mode 100644
index 0000000..3745380
--- /dev/null
+++ b/subprojects/nlohmann_json.wrap
@@ -0,0 +1,6 @@
+[wrap-git]
+revision = HEAD
+url = https://github.com/nlohmann/json.git
+
+[provide]
+nlohmann_json = nlohmann_json_dep