machine/thingplus: rename to the singular thing as that it the correct name

Signed-off-by: deadprogram <ron@hybridgroup.com>

src/machine/board_thingplus_rp2040.go

@@ -1,5 +1,5 @@
-//go:build thingsplus_rp2040
-// +build thingsplus_rp2040
+//go:build thingplus_rp2040
+// +build thingplus_rp2040
 
 package machine
 

targets/thingplus-rp2040.json

@@ -3,8 +3,8 @@
         "rp2040"
     ],
     "serial": "uart",
-    "build-tags": ["thingsplus_rp2040"],
-    "linkerscript": "targets/thingsplus-rp2040.ld",
+    "build-tags": ["thingplus_rp2040"],
+    "linkerscript": "targets/thingplus-rp2040.ld",
     "extra-files": [
         "targets/pico-boot-stage2.S"
     ]