Drop R-devel (pre 4.5.0) compatibility definitions

During the R-4.5.0 development cycle, R introduced a number of entry
points which we were required to use, necessitating checks for SVN
revision numbers for compatibility with older versions of R-devel.

Since R-4.5.0 has been released, remove the checks.

Author: aitap

src/data.table.h

@@ -13,8 +13,7 @@
 #  define RAW_RO RAW
 #  define LOGICAL_RO LOGICAL
 #endif
-// TODO: remove the `R_SVN_VERSION` check when R 4.5.0 is released (circa Apr. 2025)
-#if R_VERSION < R_Version(4, 5, 0) || R_SVN_REVISION < 86702
+#if R_VERSION < R_Version(4, 5, 0)
 #  define isDataFrame(x) isFrame(x) // #6180
 #endif
 #include <Rinternals.h>
@@ -38,8 +37,7 @@
 /* we mean the encoding bits, not CE_NATIVE in a UTF-8 locale */
 #define IS_UTF8(x)  (getCharCE(x) == CE_UTF8)
 #define IS_LATIN(x) (getCharCE(x) == CE_LATIN1)
-// TODO: remove the `R_SVN_VERSION` check when R 4.5.0 is released (circa Apr. 2025)
-#if R_VERSION < R_Version(4, 5, 0) || R_SVN_REVISION < 86789
+#if R_VERSION < R_Version(4, 5, 0)
 # define IS_ASCII(x) (LEVELS(x) & 64)
 #else
 # define IS_ASCII(x) (Rf_charIsASCII(x)) // no CE_ASCII