Remove obsolete ruby-oci8 2.0.3 TIMESTAMP patch

The oci8_patches.rb file patched a fractional seconds bug that only
activated for ruby-oci8 2.0.3. Since the project requires ~> 2.1
(and the fix was included in 2.0.4), this patch has been dead code
for years. Also bump the runtime version check to match the gemspec.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: yahonda

lib/plsql/oci8_patches.rb

@@ -14,10 +14,8 @@
   raise LoadError, "ERROR: ruby-plsql could not load ruby-oci8 library. #{msg}"
 end
 
-require "plsql/oci8_patches"
-
 # check ruby-oci8 version
-required_oci8_version = [2, 0, 3]
+required_oci8_version = [2, 1, 0]
 oci8_version_ints = OCI8::VERSION.scan(/\d+/).map { |s| s.to_i }
 if (oci8_version_ints <=> required_oci8_version) < 0
   raise LoadError, "ERROR: ruby-oci8 version #{OCI8::VERSION} is too old. Please install ruby-oci8 version #{required_oci8_version.join('.')} or later."