meson: adjust nlohmann-json dependency

Simplify the dependency logic and align wrap file directives with
other repositories.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I61209bcd25995ef447c790e59ad717c1192acbc2
diff --git a/subprojects/nlohmann_json.wrap b/subprojects/nlohmann_json.wrap
index 477e844..3745380 100644
--- a/subprojects/nlohmann_json.wrap
+++ b/subprojects/nlohmann_json.wrap
@@ -1,6 +1,6 @@
 [wrap-git]
-url = https://github.com/nlohmann/json
 revision = HEAD
+url = https://github.com/nlohmann/json.git
 
 [provide]
 nlohmann_json = nlohmann_json_dep