Remove version argument for make docs

Makefile

@@ -23,7 +23,6 @@ debug ?=          ## Add symbolic debug info
 verbose ?=        ## Run specs in verbose mode
 junit_output ?=   ## Directory to output junit results
 static ?=         ## Enable static linking
-version := master ## Specify version for docs generator
 
 O := .build
 SOURCES := $(shell find src -name '*.cr')
@@ -65,12 +64,6 @@ DEPS = $(LLVM_EXT_OBJ) $(LIB_CRYSTAL_TARGET)
 CFLAGS += -fPIC $(if $(debug),-g -O0)
 CXXFLAGS += $(if $(debug),-g -O0)
 
-ifeq ($(version),master)
-  DOCS_OPTIONS := --sitemap-base-url=https://crystal-lang.org/api/master --sitemap-changefreq=daily --sitemap-priority=0.3
-else
-  DOCS_OPTIONS := --sitemap-base-url=https://crystal-lang.org/api/$(version) --sitemap-changefreq=never --sitemap-priority=1.0
-endif
-
 ifeq (${LLVM_CONFIG},)
   $(error Could not locate llvm-config, make sure it is installed and in your PATH, or set LLVM_CONFIG)
 else