don't use format

The install command at the private repo, can't
seem to override it from the commandline then

Contributes to CURA-10317

conanfile.py

@@ -277,11 +277,13 @@ class CuraConan(ConanFile):
         self.requires("pysavitar/5.2.2")
         self.requires("pynest2d/5.2.2")
         self.requires("uranium/(latest)@ultimaker/testing")
-        self.requires("fdm_materials/(latest)@{}/testing".format("internal" if self.options.internal else "ultimaker"))
         self.requires("cura_binary_data/(latest)@ultimaker/testing")
         self.requires("cpython/3.10.4")
         if self.options.internal:
             self.requires("cura_private_data/(latest)@ultimaker/testing")
+            self.requires("fdm_materials/(latest)@internal/testing")
+        else:
+            self.requires("fdm_materials/(latest)@ultimaker/testing")
 
     def build_requirements(self):
         if self.options.devtools: