Fix regression in TinyJavadocProvider (#516)

This was param.getName using tiny-mappings-parser before #495. It was writing the method name as the parameter name, which doesn't seem too correct...

src/main/java/net/fabricmc/loom/decompilers/fernflower/TinyJavadocProvider.java

@@ -151,7 +151,7 @@ public class TinyJavadocProvider implements IFabricJavadocProvider {
 						addedParam = true;
 					}
 
-					parts.add(String.format("@param %s %s", methodMapping.getName(MappingsNamespace.NAMED.toString()), comment));
+					parts.add(String.format("@param %s %s", argMapping.getName(MappingsNamespace.NAMED.toString()), comment));
 				}
 			}